You can easily look at Gens 1 and 5 for something like that because they were planned as RPGs first, multiplayer games second.
For example, Vileplume is a straight-up worse Venusaur to give players a Grass mon to use against Misty while maintaining the starter's value.
Gen 5 has the infamous evolution level debacle specifically because of where certain mons are placed in the story, which leads to hilariously sad things like USUM Rufflet/Vullaby.
Case and point, HYDREIGON
Who in their right mind decided that Deino should evolve into Zewilous at LEVEL 50, and then again into Hydreigon at LEVEL 64!?!
The damn thing isn't even gonna get to Hydreigon unless you use it heavily in the postgame! But by then the adventure is over so there is nothing for it to really do outside of competitive!
Oh and let's not forget, in BW2 you can catch Level 25 Mandibuzz / Braviary on route 4 with their hidden abilities on the right days, like Gamefreak realized that the late game mons had horrible evolutionary requirements, but didn't feel like fixing them (or at least adjusting it from Gen 6 onwards).