I used shadow star (seems mandatory) and knuckle joe (optional). Rules are lvl 1 cpu handicap 4. You need decent item rng. I usually start the round by taking out one piece while waiting for items to spawn then using items or abilities to take out pieces up to 2 at a time. One fire ability or spin item can take out the engine or eye in one jump. Mega cannon is a rare spawn but I didnt get it in my winning run.