It really depends on the moveset, so I’ll provide one of those as well.
Starting things off, max out speed. It’s pretty important on a Raichu, since it has crappy defenses and it needs to be able to out speed the opponent to get good damage off. So 252 Speed. For the nature, I’d go with Naive/Hasty so you can boost your speed without lowering an attack stat. Here’s the full set I would use:
Raichu @ Life Orb
Ability: Lightning Rod
EVs: 96 Atk / 160 SpA / 252 Spe
- Thunder Punch
- Focus Blast
The Life Orb is for extra damage output. Lighting Rod absorbs electric attacks and boosts your Special Attack when hit by one. The EVs max out it’s Speed and make it be able to hit hard physically and specially. Hasty lowers Defense and raises speed. Thunder Punch is physical STAB. Surf is special and covers ground types. Focus Blast is special coverage. Nuzzle is to paralyze the opponent.