Oddly enough that guard you are supposed to squash can be killed realtime. My strategy was to run halfway in (about) and immediately shield twice. the first shield gets blown up by his mega zap, and he will then roll a grenade to bypass your second shield. after you create the second shield, retreat, then jump back over the grenade while still remaining behind the shield. make shields and retreat to get him to advance, then kill him with a mega blast+normal shot while hiding behind the shields.
If you get zapped by his megablast stop and shield a little earlier. if you got it right you will create the second shield just as the first one gets blown up.
very useful in a RTA speedrun because you can skip the guard guarding the drop ball completely.
The guy's tactics aren't quite good enough to force you to kill him the intended way even playing real time, though they are pretty good. In fact i first beat him in a straight up fight before i realized the globe shooting bit. And yes, this tactic works in every single version.