>>26725707I assume you specifically mean cross-gens, because regular evolutions would have tons of examples. I also won't use baby Pokémon since that's going in the wrong direction.
Poliwag gets a +115 boost into Politoed.
Lickitung gets a +115 boost into Lickylicky.
Roselia gets a +115 boost into Roserade.
Porygon gets a +120 boost into Porygon2.
Aipom gets a +122 boost into Ambipom.
Yanma gets a +125 boost into Yanmega.
Togetic gets a +140 boost into Togekiss.
Nosepass gets a +150 boost into Probopass.
Slowpoke gets a +175 boost into Slowking.
Snorunt gets a +180 boost into Froslass.
All Eeveelutions raise Eevee's BST by +200.
Kirlia gets a +240 boost going into Gallade.
There are some really shitty evolutions out there, like Electabuzz only gets a +50 boost going into Electivire holy shit, but weaker Pokémon have a better chance of getting a good evolution than a good Mega. Like if Game Freak ever shows mercy and gives Farfetch'd a Mega, how the fuck are you going to make it worthwhile? You'd have to minmax it worse than Beedrill to make a 452 BST Mega work. With an evolution you don't have any limits, they could give it something like 532 BST (which would be nice since it's 352 swapped around and fits in the range of evo BST boosts), then you might get something useable.
