Everyone knows how awful Magikarp is until it evolves. But I see Feebas get talked about way less often, though given how it isn't nearly as widespread as Magikarp throughout the series, I see why. I mean as a Pokemon it is pretty alright, but in terms of battling, it's just a slightly, and I repeat slightly, better Magikarp. Like Magikarp, all stats but speed are so low that it's comical, and good luck taking advantage of that 80 speed which is great for a first form mon when it's stats are just magikarp's with the defensive stats swapped. If you're thinking of using this in your playthrough, hope you got a prism scale and someone to trade with available, as not only are it's stats atrocious, but it has the same level up movepool of Magikarp that consists of splash, tackle, and flail. Now, unlike Magikarp, it does have a decent selection of TMs, with moves like surf or ice beam, but there's two problems. One, it's stats are atrocious, so good luck taking advantage of them, and two, it is only water, ice and normal moves, that's it. No stat buffing moves to make it less terrible aside from the absurdly common double team, and toxic is the only way to use this thing to damage without relying on it's pitiful stats aside from hail, which I think I don't need to explain why you won't use that on this.
I understand that this thing is kinda supposed to suck in terms of battling, and yeah Milotic absolutely does not suck, being a great defensive wall which can do decent damage both passively and aggressively, alongside recover, but unless you got a prism scale and someone to trade with available, this thing is horrible incarnate, just being Magikarp but slightly better. Also, it is insanely hard to get in gen 3 and 4, and even in games where it's easier to get like the gen 7 games it isn't exactly easy to get. So if you're thinking of using this for an intentionally bad team as a challenge... Good luck finding it.