Ravenous Slime

• WWizards of the Coast2018-07-13
  Official Ruling
  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.
• WWizards of the Coast2018-07-13
  Official Ruling
  The exiled creature's last known existence on the battlefield is checked to determine its power.
• WWizards of the Coast2018-07-13
  Official Ruling
  A token creature can die just like a nontoken creature before ceasing to exist. Ravenous Slime can replace this by exiling the token.
• WWizards of the Coast2018-07-13
  Official Ruling
  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.
• WWizards of the Coast2018-07-13
  Official Ruling
  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.
• WWizards of the Coast2018-07-13
  Official Ruling
  If Ravenous Slime dies at the same time as an opponent's creatures, the opponent's creatures are exiled.

Rulings via Scryfall