Reign of Apocalypse reads

To play, exhaust and Apocalypse you control.
KO target character if there are no characters with lower DEF in play.

Now... I'm a little confused on how to play this card...

number 1 I have to exhaust Apoc.. that's easy.
now... the KO condition... if there are no characters with lower DEF in play.

now I know this is for both me and my opponent... but I'm confused on the comparison. Is the DEF being compared to apoc or what?

Because there will always be a character (unless there are no characters) with lower DEF in play.

Actually all you do is after you exhaust Apoc., you target a character. (yours or your opponants) Then you just compare his Def to EVERY other character on the field. (even Apoc) If it's Def is lower then everyone else, it gets KO'ed. If it's not it stays. There are effects that in response to this card being played can lower or raise the defense. You play them accordingly and them compare the defense to everyone else.