Synchronization

Full Synchro(nization) is a state where NetNavi and NetOp become one to improve focus and it puts the NetOp into direct contact with his/her NetNavi, transmitting effects on the NetNavi back to the NetOp. So, a high level of synchronization should complete the circuit enabling transmission of a NetOp's very will to his/her NetNavi, which greatly raises a NetNavi's fighting capabilities. FullSynchro fuses the mind of NetNavi and NetOp into one consciousness, getting rid of the delay between command and reaction, which can make a big difference between life and death during a battle.

Games
In the game, Full Synchro is first introduced in the final part of MegaMan Battle Network 3, and is available in the game mechanics of MegaMan Battle Network 4 and onwards. Full Synchro can be obtained when hitting an opponent with a chip attack while the opponent is in the middle of its attack animation. This is called "countering", and it also paralyzes the countered opponent. In MegaMan Battle Network 4, Full Synchro could also be obtained by performing well, hitting the opponent repeatedly without getting hit, but this may have been removed for balance reasons. Full Synchro allows the player to see when an opponent can be countered (in order to maintain Full Synchro throughout the battle) and awards a x2 damage bonus to the currently selected chip. However, it can be lost when the Navi is hit or uses up a damaging chip without countering again.

Anime
In the anime, synchronization between NetNavi and NetOp is needed to perform Cross Fusion.

Manga
In the Megaman NT Warrior manga, Full Synchro works much like how it is described, fuses the NetOp and NetNavi into one consciousness, but unlike other canons differs majorly in one way: Whatever happens to the NetNavi in their world, happens to the NetOp in the real world. (i.e. if your Navi gets slashed, you get a slash wound on the exact same spot) However, unlike game canon once a NetOp and NetNavi successfully do a Full Synchro, they can do it again at will as well as undo it at any time (usually when the battle is over or the battle is becoming too risky).

Also, Perfect Synchro has been thought of as the last state available in Full Synchro. It's ultimately Full Synchro at 100% (which removes all delay from the NetNavi's battle routine). However, this renders the NetOp's body in the real world to be soulless- in the state between life and death.