If my opponent uses Guzzlord's "Red Banquet" attack and my Active Pokemon with Big Parasol attached gets KO'd, does my opponent get to take an extra prize for "Red Banquet" or not?

Big Parasol prevents all effects of attacks from your opponent's Pokemon done to your Pokemon; but taking an extra prize is a game effect, not "an effect done to your Pokemon", so your opponent gets to take the extra prize.

Relevant cards

SM12_136

SWSH3_157