Is there such phrase as "what more"?
Solution 1:
I'd say:
If Canelo can do that to Khan, imagine what Golovkin can do.
Imagine if Michael Phelps had competed.
'what more' : I've apologized a thousand times - what more can I say?
Solution 2:
For your intended purpose, it's better to use "what's more", defined by TFD
the next fact is at least as important or even more important.
"Military action will hurt ordinary people, and what's more, it won't solve the problem."
I hope this helps. What more would you like to know?