Grovyle has the signature move Leaf Blade. It's a 70 power Grass move. It's arguably worse than Giga Drain, which while that has 60 power it heals half the damage inflicted. There's two ways to get Giga Drain of Grovyle. One is to use TM19, a one time use item. The other way is to level Treecko to 46. Don't worry, that still gives you time to evolve into Sceptile and gets its final level up move at level 59, False Swipe, which has 40 power and cannot kill.

Sharpedo, a Water and Dark type, doesn't learn any Water type attacks from level up. It also has 25 more points in Attack than Special Attack. At the time, Water and Dark type moves were were special attacks. If you think it's dumb to make a Water/Dark physical attacker in Gen 3, don't worry, they did the same thing with Crawdaunt, who has 30 more points in Attack than Special Attack.

The only Grass type move the Shiftry line learns via level up is Synthesis, a non-damaging move. However, you only get this if you don't let Seedot evolve at 14 and instead train it to 21. Its only Grass attack options are the TMs for Bullet Seed, Giga Drain, and Solar Beam. Also again, Grass and Dark are special attacking types, and Shiftry has better Attack than Special Attack.

These aren't nitpicks, there's tons of Pokemon like this. This is mostly a great game, but has some very odd design choices.