I think Cannonball was carrying the teradectal when he got him. When he touches you with his body while he's not blasting he takes you within his shield therefore he is unprotected from anything within it.
I mean...Cannonball was made to blast through buildings. Look at that thing comming out of Ego's right eye. Does that look like a boo boo.
I understand his shield provides him with thermal nucular protection...but there is a scale that applies to these things.
Just like Prof. X can be beat by a better telepath. When a guy hits his limit...that's it. No more argueing or anger or bargining, i.e. wanna do this or form a team so to speak. That's all bullcrap. If you don't believe me yet and need to keep pretending you don't understand go take the pretend test of dropping a 40 pound weight on your hand. I bet then you'll really want a doctor and one won't appear for you either. Youll really have to get to a hospital somehow.
Anyhow...Ego wouldn't even fight him. He'd just create a few hundred 100ton class...you know guys like the Hulk and Surfer. Then Cannonball can preach his theory of the open hand or the closed fist. I'm sure with his kind of charisma he'd have a whole new fighting team...whadda ya think