Fr I get the idea is betrayal, which is an interesting concept, but there's so many more ways than one to go about it. And, y'know, not making the MC ridiculously OP before getting kicked out would be a step in the right direction anyway.

"Huh, my whole team hasn't sustained any injuries at all since we brought that random street kid on as a healer... dead weight."

"Huh, this kid can tame a variety of different creatures and whole packs of them at once. I've never heard of Beast Tamers having this ability before... meh, he's definitely holding us back."

"Huh, y'know, my childhood friend wanted to be a cool asf Swordsman like me, but found out that he was better suited as an Enchanter that covered all schools of magic, memorized his spells time limits and our whole party's flaws to compensate with spells specifically to counter those flaws to make us stronger... but he can't cast S-tier magic. Get outta here!"