This Article shows the main nerf's throughout the generations.
Also, this (credit to sumwun for the list!!) is a bigger list that showcases move changes.
Please tell me if there are some that I missed which weren't in the Article.
Extras which weren't in the article:
1. Hyper Beam Nerf: In Gen 1, Hyper Beam, if it knocked out the opposing Pokémon, would have no recharge.
This was changed in Gen 2, where Hyper Beam always had a recharge, regardless of the opposing Pokémon being knocked out by it, or not.
Hope it helped!