A combo can be any set of cards which effectively ends the game in your favor, be that a prison like Teferi + Knowledge Pool, infinite damage/mill, or even a very fast combat clock like Skithiryx, the Blight Dragon + Lightning Greaves
Having Sakashima of a Thousand Faces enter as a copy of your other commander also makes it so that if your coin flips are good enough, you can have a copy of the spell resolve while you also have the original spell return to your hand when each of your commanders get different coin flip results
Having an eldrazi as your commander unlocks the potential of a few powerful cards that dont work in most decks
POKEMON OBF EN-OBSIDIAN FLAMES
Another expensive pickup is Zeraora-GX LOT 86, an Electric-type that removes the retreat cost on any of your Pokmon that have Lightning Energy attached
Next, green players may find themselves playing Primal Might -- a removal card blended with a temporary boost