Eevee to Leafeon: Mossy Rock in Generations 1 - 7, Leaf Stone in Gen 8
Eevee to Glaceon: Icy Rock in Generations 1 - 7, Ice Stone in Gen 8
Eevee to Sylveon: High Affection in Gens 1 - 7, high Friendship in Gen 8
Charjabug to Vikavolt: Level up in a magnetic field in Generations 1 - 7, Thunder Stone in Gen 8
Magneton to Magnezone: Level up in a magnetic field in Generations 1 - 7, Thunder Stone in Gen 8
In Gen 3, you didn't need a Pokeball to get Shedinja. In Gens 4 and up, you do.
Feebas to Milotic: You needed to max out Feebas' Beauty stat before Gen 5. Starting in Gen 5, you could also evolve it by trading it with a Prism Scale.
Several regional variants -- which are arguably the same Pokemon, as they occupy the same slot in a Pokedex as their original forms -- have also changed evolution requirements.
Alolan Rattata needs to be levelled up to Level 20 in the night, rather than at any time.
Alolan Sandshrew needs an Ice Stone, it doesn't evolve via level up.
Alolan Vulpix requires an Ice Stone, not a Fire Stone.
Alolan Meowth needs high Friendship to evolve, it doesn't evolve via level up.
Cubone must be level 28 at night in Alola to evolve into Alolan Marowak, not just level 28
Galarian Slowpoke needs to be traded while holding either the Galarica Wreath or Galarica Cuff, it doesn't evolve via level up or by trading with a King's Rock.
Galarian Darumaka requires an Ice Stone to evolve.
Galarian Yamask must be walked under an arch after taking more than 49 Hit Points of damage.
Hope I helped!
