X Challenge

X Challenge is a mode exclusive to the Mega Man X Legacy Collection and Mega Man X Legacy Collection 2 which allows the player to simultaneously fight two bosses from the SNES and/or PS1 Mega Man X games (X1-X6) using X in three consecutive battles. Volume 1 is part of Mega Man X Legacy Collection and Volume 2 is part of Mega Man X Legacy Collection 2. The final match for each of these stages is version-exclusive.

In addition, the mode contain an exclusive armor (a variation of the Ultimate Armor) which players have option of using X with or without it equipped. Each challenge will have 9 possible special weapons from the six X titles which players will be able to choose between 3 of them. They cannot be swapped until all three challenges are completed. X will also have use of Zero's Z-Saber much like in X6. By not selecting any special weapons before a challenge, a Buster-only mode is activated where X only has use of his X Buster (with the Z-Saber as a sub-weapon). In addition, this mode will also remove most of the armor, excluding the Foot Parts, leaving X with just the Air Dash and Hover abilities. The only difference between difficulty levels is the amount of damage that can be inflicted between both X and the Mavericks

Much like with the Challenges from Mega Man Legacy Collection and Mega Man Legacy Collection 2, each challenge has a clock system and a leaderboard system for players to compete by completing the challenges as quick as possible and within the time limit which is 10 minutes.

Unlike with the earlier Legacy Collections however, players only have a limited amount of lives and start with 2 extra lives in reserve when beginning the challenge, and cannot be restored to full health between challenges. In addition, weapon energy cannot be restored as well. In Easy Mode however, defeating the first boss among the pair can earn the player a Large Energy capsule and also allows for the Weapon Energy of all weapons to be restored between challenges.

Once the player completes X Challenge, Hard Mode is unlocked. In addition Practice Mode becomes available, which allows for the player to participate in a single challenge regardless of difficulty. However,

Completing 9-3 on Hard Mode will grant access to level 9-4, a secret level in which the player must fight both Ultimate Armor X and Awakened Zero. In this level, instead of getting a Game Over if the player is defeated, the game will instead skip to the credits - even though the player starts off at 100% with all lives, energy and weapon energy restored, just like a normal challenge. 9-4 is excluded from Practice Mode due to it being a secret level.

Strategy
Though fighting these three Consecutive battles is tough and that X will only have three special weapons, the trick is to figure out which of the two bosses is the larger threat and just focus on using their weakness against them, while attacking the other one with X Buster since the Plasma Ball can help deal with inflicting minor damage and destroying minor obstacles. The Z-Saber, while effective against Zero Nightmare, should only be reserved for dealing with quick damage and minor obstacles. Occasionally special weapons may help against other bosses, such as Gravity Well against the Blaze Heatnix/Blast Hornet challenge.

Also when playing on Normal or Hard Mode, if X's health is high enough after completing a challenge, it is possible to complete another challenge to help conserve remaining lives, otherwise just waste the rest of X's life energy if his health is too low to avoid wasting weapon energy.

To get the achievement/trophy "Speed of Light" from Mega Man X Legacy Collection 2 which requires the challenge to be completed in less than a minute, a great method is to go to Shield Tactics - Stage 7-1, Armored Armadillo and Rainy Turtloid's stage - and bring their weaknesses, Ice Burst and Electric Spark. Electrick Spark's charged form can not only dispose of Armadillo quickly, but it also easily destroys the gems in Turtloid's shell, making him much more vulnerable to Ice Burst. However, in Easy Mode, there are more opportunities to complete this achievement due to the fact that bosses take more damage from X's special weapons. For another achievement from Mega Man X Legacy Collection 2 "Can't Hit Me", which involves completing the challenge in under 3 minutes, the trick is draw it out by leaving one boss behind whose attacks are easier to deal with such as Bubble Crab (due to being able to stay in the air above him) or Storm Eagle. For dealing with the "Elite" achievement from Mega Man X Legacy Collection, it is better to do it with Stage 1 since the bosses there are not really as difficult and it is easier to use effective strategies to beat them.

If completing the X Challenge is too difficult at higher difficulties, then it would be easier to complete the X Challenge on Easy Mode first. This way it makes easier to complete the game and also to unlock Practice Mode. Practice Mode can be used as an effective means of training, to help train players for completing challenges at higher difficulty levels with the exception of 9-4. In addition, using Easy Mode can make it more effective to collect all the Hunter Medals exclusive to X Challenge as there are no difficulty level requirements for earning them.

Changes in X Challenge
There are some differences in X Challenge, which was due to a number of factors that were changed (stage factors, weapon usage, boss attacks etc.) when compared to their original release. Some of these changes were made due to the SNES bosses mixed in with the PS1 bosses/gameplay features or to level the playing field for X Challenge to make it simple to avoid gaining too much of an advantage over the bosses. These changes includes:


 * In Stage 9-1 (Power Saw - Spark Mandrill and Rainy Turtloid's stage) the battle room is larger than normal. This is to account for the extra room needed to avoid Turtloid's attacks.
 * Zero Nightmare is slightly altered in X Challenge mode (Normal and Hard); (1) he always has the Thousand Shots attack available regardless of his health. (2) He will use the level 4 variation of Gemurei Kai slashes which he shoots 4 slashes instead of 3, a locked feature in the original game that can only be seen via external cheats/game data modifiers. (3) He has additional laugh voice clips (recycled from intro laugh voice) during ground dash. (4) He can be stunned by jump saber slashes in his initial/dash stance while he can only be stunned by ground slash in the original game.
 * Damage output of several attacks including Sigma's electric spheres, Zero Nightmare's dash contact/Saber slash is modified to be abnormally high (one direct hit of saber slash removes about 1/6 of X's health bar in Hard) - presumably a development oversight.
 * Speed Burner and Strike Chain are nowhere as effective as in original game mobility-wise; because the action system of X is similar to his X6 incarnation and X will not retain increased speed after performing air dashes.
 * The sphere generated by Plasma charged shot is able to damage X5 and X6 bosses but this change makes the main part of charged shot harder to directly hit bosses, in most cases the weaker damage of Plasma sphere will land on bosses first and they won't take damage from the main part of charged shot.
 * The boss invincibility system is changed; bosses will deflect uncharged X buster pellet during invincibility, this makes the rapid uncharged shot strategy against several X1-X3 bosses (especially Neon Tiger) harder to execute and less effective because X can't shoot more than 3 pellets in a row and can't fire new shots until deflected uncharged shots leave the screen.
 * The Strike Chain lock up strategy against Wheel Gator from the original game is not possible here due to the changed invincibility system.
 * In Web Spider's arena, the moment X is allowed to move is later than in the original game; this is probably done in order to avoid the situation which Web Spider being glitched by taking charged Twin Slasher before the fight actually starts.
 * Using charged Strike Chain as finish blow on a particular boss is the only method of gaining life recovery item in Normal and Hard difficulty, but this method is not very effective - because there are only 3 special weapon slots and not every stage has Strike Chain available.
 * Unlike the original game, charged Gravity Well can be charged again right after releasing, render this weapon much more powerful and effective than in original game which can almost permanently lock up bosses weak against it.
 * Charged Ray Arrow and Charged F-Laser are given a much higher ammo consumption than in the original game, render these weapons useless in most scenarios.
 * Charged Chameleon Sting is also given a much higher ammo consumption than in original but X can now shoot uncharged X Buster pellets during the invincibility intact, which is useful to chip damage bosses in Dynamo/Gate scenario and Special Battle.
 * Ammo consumption of charged Ground Dash is also higher than original; it's useful to quicker dispatch Blaze Heatnix but the weapon ammo is not enough to completely lock him up in hard mode.
 * It's more difficult to avoid bullet attacks of SNES bosses like Neon Tiger's ground Ray Splasher and Vile's paralyze sparks because the PS1 incarnations of X's hitbox is far bigger than his SNES incarnations.
 * Chill Penguin's blizzard generator now has wind physics and will push X back, like with Storm Eagle's attacks.
 * Metal Shark Player can perform all his available summon variations in hard difficulty.
 * When playing as unarmored X (Starting a challenge with no special weapons equipped) the Z-Saber is purple instead of green like it is normally. This was done for the fight against Vile MK-2 and High Max on stage 3-3 (Volume 2 only). High Max can't be damaged without the use of special weapons, so the Z-Saber counts as one if you didn't bring any.
 * Awakened Zero's Instant Death move Genmurei has been removed.

Trivia

 * Every third stage in X Challenge is different between the two volumes of Mega Man X Legacy Collection.
 * In addition, the bosses of every ninth stage are found outside of the standard eight levels of the games in which they appear.
 * This is the only gameplay feature where X can fight against Iris, a Zero-exclusive boss from Mega Man X4.
 * Oddly, Iris still says, "Forgive me, Zero!" before her battle, despite the fact that she isn't fighting Zero. This is most likely an oversight by the developers.
 * This is also the only gameplay feature where X fights another version of himself.
 * Twelve Mavericks from the first three Mega Man X games do not appear in this mode. Those Mavericks are Launch Octopus, Boomer Kuwanger, Sting Chameleon, Flame Mammoth, Overdrive Ostrich, Flame Stag, Crystal Snail, Magna Centipede, Volt Catfish, Crush Crawfish, Gravity Beetle, and Blizzard Buffalo.
 * Coincidentally, these are half of the Mavericks from each game.
 * Sting Chameleon and Magna Centipede did appear in this mode but as copies summoned by Metal Shark Player.
 * In both iterations of stage 9-3, after defeating one particular boss, another character appears briefly and uses an attack. They will disappear each time they finish their attack.
 * In Volume 1, if Double is defeated first, Colonel appears to help Iris with any of his attacks.
 * In Volume 2, if Dynamo is defeated first, he'll later appear on the right side of the level to support Gate with his Earth Gaizer Kai attack.
 * Stage 9-4 has a somewhat similar gimmick that depends on which character was defeated first. If Ultimate Armor X is defeated first, Awakened Zero will turn into Black Zero and gain many new attacks (most of which are based on Zero's special techniques seen in X4, X5, and X6). If Awakened Zero is defeated first, Ultimate Armor X will start using new attacks based on special weapons from X6, including Yammar Option and the charged versions of Ray Arrow and Guard Shell
 * The Stage 4-1 description is a reference of SNK's Art of Fighting games, a rival series of Capcom's Street Fighter series.
 * The X Challenge game over/failed theme is a remix of Street Fighter 2 game over jingle.
 * During the Ultimate Armor X and Awakened Zero challenge on stage 9-4, X can also switch between the Fourth Armor, Falcon Armor, and Shadow Armor to perform different attacks before reverting back to the Ultimate Armor.
 * Gate has a special intro voice clip lifted from the voiced dialogue sequence of X6 which he praises X's ability of defeating his star creations and reaching his secret lab in the original game. Player must switch the game language to Japanese in order to activate the special voice clip, otherwise Gate will remain silent during his boss intro as well as during the battle.