Salamencetrainer34, either the thunder or the fire attack, yes. Thunder hits the row and column directly in front of his face; Fire hits 7 squares in a breath pattern, excluding only the top and bottom right squares.
One thing you should know is that Gregar, unlike any other enemy in the game, has TWO hitboxes: his head, plus the panel directly behind it. Thus if you use a chip like Bass, and it would hit both squares, you deal twice the damage. Chips like KillerMan and I think ChargeMan are like that too.
This makes his 2500 HP significantly less daunting.