Gen 1
Best: Vaporeon
Worst: Jynx. Just... no.
Gen 2
Best: Furret
Worst: Aipom. Really don't like primates, and especially don't like these after Detective Pikachu.
Gen 3
Best: Absol
Worst: Nuzleaf. God, I hate it's stupid nipples. I have a shiny one that I hate.
Gen 4
Best: Lucario
Worst: BURMY. STOP SPAMMING PROTECT AND LET ME MURDER YOU
Gen 5
Best: Krookadile
Worst: Munna. A foetus is not a good pokemon. That's just *ew*
Gen 6
Best: Xerneas or Sylveon
Worst: Aromatisse. No...
Gen 7
Best: Golisopod/Necrozma
Worst: Oranguru/Passimian. See gen 2.
Gen 8
Best: I kinda like Zacian's and Centiscorch's designs
Worst: Chewtle. DISGUSTENG