There are some examples that come into my mind...
1.Octillery: Having a decently high Atk and SpA (both of them at 105 base power) grants to it a good amount of fire-power, plus, Octillery's movepool is very wide, having moves from almost every type like Flamethrower, Seed Bomb, Ice Beam, Hydro Pump, etc. The only problem is its terrible speed, but that's not something that Trick Room or a speed swap in a double battle can fix, right?
2. Victini: 600 in total stats means a lot, doesn't it? And just like Octillery, its movepool's very wide. It doesn't has any attacking Water moves, tho, but I assume that isn't a problem for such strong Pkmn.
3. Delphox: Although it stands under the shadow of Greninja most of the time, the Fire-Psychic starter of Kalos can be still viable (assuming you're outside of gen 8, because it's not in Sword & Shield). its SpA (Delphox's highest base stat, with 114 base power) SpD and Spe are quite good, it has a quite decent movepool despite lacking some types. Grass Knot's a good move to have on it, considering how light it is compared to most of the Water, Rock, and Ground types it faces (it may not be the strongest, but hey: it gets part of the job done).
4. Infernape: (again, I'm assuming here that you aren't in Galar) another starter that comes in handy in some cases, Infernape's mixed movepool gives to it a wide variety of attacks to choose just like Octillery. While it can't learn any Water moves, having acces to so many moves like Close Combat, Earthquake, Poison Jab, U-turn, Stone Edge, and others can help you keep an advantage against your foe (if you play it right, of course).
If you ask me, Infernape it's your Go-to-choice outside of Galar, but if you're in Galar... well... use or try to get Victini if you can.
