ok so monster hunter says you get +1 to attack/damage vs.

ok now here is the question since we are on this trend
yellowjacket gets his giant SP where it says

GIANT MAN: Yellowjacket possesses the {giant} damage symbol and can use Charge.

if he cancels his power does he still have the symbol like a giant?

or is he safe from the monster hunter at this point?

When the power is canceled, he does not have the symbol.

but he is still really ugly with that green face and striped chin...
can´t we consider it a monster?!?

no??? darn!

Yep. Whenever a SP gives a power or symbol, cancelling it would remove anything given as if it doesn't exist on the dial.