Juggernaut, VOY 5
The Malon (one of the few memorable Voyager baddies) are back and this time they’ve brought moral complication with them!
Really a B’Elanna episode as she learns to use her natural inclination toward hostility for good. Added benefit: the first time we actually see a Sonic Shower! (BTW, is the Sonic Shower an invention of Trek Lit that made its way into the show? I think it may be.)