Track: At the beginning of the game, choose an opposing character. When Predator X is given a move action and ends his move adjacent to that character, that is a free action instead. That character receives -1 to break away rolls when adjacent to Predator X. If that character is KO'd, choose another opposing character.

Forced Evolution: Modify Predator X's attack and defense values by +1 for each other character named Predator X that has been KO'd this game.

Can Predator X choose one character, say "Spider-Man", and then use Track against all opposing Spider-Men?
No. Whenever you are told by a game effect to "choose a character", you need to choose one, specific and singular character. So if you choose your opponent's Spider-Man #1, you will not gain any benefit from Track against Spider-Man #2, #3, #4, and so on... only against Spidey #1.

Say Predator X is adjacent to an opposing character and I want to move it, via a move action, to be adjacent to the character I chose with Track. If the break away roll fails, do I need to put a token on Predator X?
Yes, you must place an action token. The move action is only a free action if Predator X ends the movement adjacent to the chosen character. In the situation described here, Predator X does not end the movement adjancent to the chosen character.

If I am playing multiple Predator Xs and some of them have been KO'd and then brought back into the game (say they were using the Lazarus Pit feat), how does that impact Forced Evolution?
First, you need to make sure the Predator Xs in question were actually KO'd. Some game effects, like Lazarus Pit, do indeed return a KO'd character back into the game. However, other game effects might say "when a character is KO'd, do X instead"... in that case, there isn't an actual KO (X occurred instead of the KO) and Forced Evolution would not be activated then.

Once you have made sure the Predator Xs were actually KO'd, then any remaining Predator Xs would get to modify their attack and defense values. Even if the formerly KO'd Predator X returns, you'd still get to modify the other Predator Xs combat values since nothing in Forced Evolution indicates that the modifier goes away.

Please keep in mind that Forced Evolution does say "each other character named Predator X". This means that a Predator X that is KO'd and then brought back would not modify its own attack and defense values.