Some argue that these consistently powerful strategies involving combo elements arent always fun to play against and may not be in the spirit of Commander, but I think setting clear expectations with your playgroup will help curb frustrations
Umaro, Raging Yeti* Straight to you from the World of Ruin in the Revival Trance Commander Deck, Umaro is a beast of a design as a 6/6 for 6 with trample who will either pump your board, shoot something, or wheel you each turn at random
In this regard, it perfectly captures the Drowzee evolutionary line and is one of the best Hypno cards of all time
Abyssal Persecutor led to such interesting game states, and Id argue this one is even more entertaining
Honorable Mentions Before I mention the un-set cards, Jumbo Cactuar has the humble printed power of 1, but it's attack trigger sends it soaring over the other cards on this list as it reaches 10,000