Gonna go with Thor pretty solidly. BB's a non-factor. The other three would have a chance with co-ordination, but Osiris is a rookie hothead who relies heavily on his power, and Thor's going to take advantage of that to take him apart. M'gann and Cassie can put up some fight but stand little chance of actually putting him down.
I'm going to say Titans, because Miss Martian is soo f*cken cute!!---> Hello Meggan... Seriously, she's done well against Supergirl, pwnd Mammoth with telepathy and a formadible opponent. Add Wondergirl, Osiris and BB, I say the team has a shot..
Agreed, individually Thor outmuscles everyone. But when their four powers combine, their a threat .... Miss Martian is mid herald at best, and Cassie isn't far behind. Add Beast Boy and Osiris, and the team might take a couple of wins.
Cassie and Miss Martian are nothing to Thor. Distractions at best. Beast Boy is even more worthless. Meggan's only saving grace is telepathy and I don't remember enough of it to comment on whether or not it would be a threat (I doubt it though since I don't remember any big feats). It all comes down to Osiris. Last I saw of him, he was getting handled by Croc. I know he had a phobia due to the horsemen, but damn. I heard he held his own against the new Captain Marvel recently so maybe he can give the team a shot....
I can't recall M'gann ever using telepathy to control an opponent, hinder someone's movements, or attack them psychically. Even if we assume that she has comparable power to the known White Martians in continuity, she's not as opportunistic or ruthless with her powers.
I imagine at best she could use it to predict his actions and coordinate the team.
Freddy Shazam doesn't really impress me in the least. He's supposedly as powerful as Billy in his prime as Captain Marvel, but he just got his powers stolen somehow by Osiris...even though that doesn't make sense to begin with.
She was messing with his head.. He was seing cute bunnies everywhere.
Meggan took him out rather easily. If she was written that way, the Titans wouldn't have a hard time with their opponents. Also, she held her own against Wyld a creature created by Raven and read Bombshell's mind all the way from Australia.