Yes, that is indeed Squall using the Renzokuken on a Behemoth. He has the Lionheart equipped, which is of course his ultimate weapon, so there's a 25% chance that his finishing move will be the Lion Heart which is the second strongest Limit Break in the game. It hits seventeen times and judging by the damage numbers in the gif it is highly likely that most of those hits will do quad nine damage so that Behemoth is very likely dead. Though watch out, as they cast Meteor on death and that could prove fatal.