A token creature can die just like a nontoken creature before ceasing to exist. Ravenous Slime can replace this by exiling the token.

The exiled creature's last known existence on the battlefield is checked to determine its power.

If Ravenous Slime dies at the same time as an opponent's creatures, the opponent's creatures are exiled.

If more than one replacement effect tries to change where a dying creature ends up, that creature's controller chooses which effect applies. For example, if two players control a Ravenous Slime, a creature controlled by a third player will be exiled by the Ravenous Slime of that third player's choice, and the other Ravenous Slime won't get +1/+1 counters.

If an opponent's commander would die, that player may choose to put it into the command zone from exile after Ravenous Slime's replacement effect has been applied and it has received the +1/+1 counters.

Once a creature with power 3 or greater has blocked this creature, changing the power of the blocking creature won't cause this creature to become unblocked.