If you limit it strictly to X-Men v. Justice League, Prof X's kids would pull it out. But if you expanded the battle to the entire Marvel and DC universes...
He gave us a blank map of south america and it said "denote and label the regional climates of south america in accordance with the Koeppen scale". I filled in as many as possible and wrote "the anteater always wins". The rest of the test was solid, just immense as it took the entire period to finish.