Neo. X, or Robot Y in PAL and US versions of Streets of Rage 3, is one of the final bosses in Streets of Rage 3, appearing in Stage 7 of the Good Ending route.
Neo. X is controlled by the disembodied brain of Mr. X. It moves with a few jetpacks attached to the shoulders and attacks by charging, throwing the player, firing a volley of missiles at them in long range, and also using a crushing grip on them. Neo X can catch players in mid jump and will always land on its feet when tossed.
To get the game's best ending, the player must defeat Neo. X under three minutes. If they fail to defeat Neo. X in time, they'll get one of the bad endings.