Gen 1: Lickitung and jynx? geodude is also ugly
Gen 2: I find sunflora ugly
Gen 3: tbh slaking, but salamence is kind of ugly too for his generation
Gen 4: mothim, lickilicki, rhyperior (but he's growing on me?) magmortar, probopass, heatmor. Sorry I think this generation has the ugliest pokemon overall
Gen 5: unpopular opinion, but I LOVE emboar, klinklang, garbodor, stunfisk, druddigon and them. I do find simipour, simisear conkeldurr and palpitoad ugly af
Gen 6: I think the slurpuff line is some of the ugliest pokemon ever
Gen 7: komala. Not the ugliest pokemon ever but so darn boring and not even cute
Gen 8: Arctovish, hands down. But Arctozolt is kind of awkward too. Yamper looks ugly and is saved by evolution