I don't really know that much about Spawn, but from what I hear, he's a real contendah.
Apocalypse has an edge in cunning, but Lobo's a sick bastard, and I can't decide who would win between the two. Probably Lobo's tougher.
Then Lobo would be all like "Yo! Supes! Your wife's a tart!" And Supes would be all like "*Sob, sob, sob*"