Crumbling Colossus

Oracle Text

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

When Crumbling Colossus attacks, sacrifice it at end of combat.

Card Rulings

9/22/2011 If another player controls Crumbling Colossus when its ability tries to resolve, you’ll be unable to sacrifice it. It will simply remain on the battlefield.