Why did Ryze think the power that Xerath wields is feeble?

power was never meant for him, therefore being unworthy of such power, must've somehow realised that and obviously was salty and decided to be bully

He might have seen the idea to give up your body for more power as something foolish

Though I think the real reason was likely that Riot wanted Ryze to look wiser than Xerath

Xerath power has always been shown as something unstable and it's common agreement that Xerath focuses a lot to keep his form intact. Ryze probably thinks that Xerath won't be able to hold on it for too long (too bad he survived millenia already). Ryze has always been some1 that thought high about himself and his powers hiding behind false modesty.

Where does Ryze say this?