Weird alien dude on a flying sled: heroes were just expected to deal with that in the 70's.

Even the guys you wouldn't expect to deal with aliens had to deal with aliens then, because UFO's were big, and writers could probably get at least an issue out of it if they were stumped. Can Swampy put his own spin on it? From 1976, Swamp Thing #21, "Requiem" Written by David Michelinie, art by Nestor Redondo.

Swamp Thing is abducted by alien creep Solus, an exile on a massive ship who kidnapped slaves to amuse him from various worlds. While Swampy gets locked in a tube--which I think happened a lot in his series--Solus tells his story to his favorite, the winged girl Cellanth; who was trying to string him along long enough to get at his control device. He had been royalty on his world, but was condemned for killing his brother: Solus claims his brother had been a poor ruler, weak on affairs of state, but it's pretty obviously just ego. For his crime, he was not only exiled in his ship, but also had nodules embedded in his skin that would go off "at the slightest touch of planetary soil!"

Cellanth does free the other aliens, but their escape hits a snag when Solus controls Swamp Thing, using him to kill several of them before they can transport away. Solus then forces Cellanth to dance herself to death, but then immediately regrets it. Rather than admit that he, 'a god,' made an error; he kills some more innocent aliens before Swampy is able to knock his control device out of his hand. The remaining aliens, somewhat charitably, decide against killing Solus, instead planning to leave him stranded and alone, as they thought that would be worse for him. Panicked, Solus goes for his control, but misses and looks like he's going to fall into space. Swampy feels bad and tries to save him, but Solus grabs him; intent on controlling him again. Instead, his self-destruct nodules activate, as Swampy was "made of...planetary soil...!" Solus drifts away and explodes, and Swampy beams down to somewhere in the western states, thinking he understood a bit about what had driven Solus mad; although I don't think Swampy knew the guy was maybe a jerk before that.

I kind of like that explosion panel, although I think that could've been slotted into any number of Swampy's stories from this run: he was kind of on the same plot engine as the Hulk, where somebody messes with him and gets wrecked for their trouble.