Well it seems that gorillas and elephants make a strong case for powerful "vegetarians"
How many vegans complete in "worlds strongest man" competitions and does well? How many weightlifters, powerlifters, bodybuilders, fighters. You will find that there are a few, usually to prove some ridiculous point of "it can be done" (living on bread and water can also be done, but...lame point).
The worlds currently strongest man (probably the strongest man ever on record) eats:
Breakfast: Milk, cornflakes, eggs, youghurt, cheese.
Lunch: Fish, rice, vegetables, juice.
Dinner: Meat, potatoes.
http://www.theworldsstrongestman.com/zydrunas_savickas.phpa shitload of fat and proteine.....ofcourse
edited: How about bodybuilders.
Elite Vegan bodybuilder vs. hobby carnivore bodybuilder
vegan BB'er Robert Cheeke. Good job with what he has to work with I reckon.

Kim Kold. Got some titles under his belt, but not enough to declare him elite of any sort

Compare with elite carnivores
Jay Cutler - Big on fish

Macrus Ruhl

and one of my own personal "heroes" nasser el sonbaty.

Can you spot the difference?