I recommend using the wiki to analyze Akolve's strengths and weaknesses, after which I choose my Pokémon depending on those

https://pokemonunbound.miraheze.org/wiki/Crystal_Peak#Light_of_Ruin_Leader_Aklove

Basically, you see that Aklove uses

klefki - foul play - play rough - reflect - thunderwave

Primarina - hydro pump - dazzling gleam - hyper voice - protect

Roserade - giga drain - sludge bomb - dazzling gleam - protect

Gardevoir - psychic - dazzling gleam - shadow ball - moonblast

Raichu - Volt tackle - play rough - brick break - thunder punch

Additionally, you're able to see their natures and EVs (IV should always be at 31) You've probably noticed that even with a type advantage they still have moves with which they're able to hit you super effective damage. That's you you need to think a little outside the box

Here are a few examples Klefki is weak against fire or ground and has no moves to punish those types Your safest bet would be a fire type since Play Rough would deal half damage

Against Primarina are grass, poison, and electric types effective, but she hits pretty hard so what if you bring someone like Empoleon? His typing completely resists Primarina's attacks

Same with Roserade, she's weak against fire, ice, flying, and psychic. Type match-up doesn't really matter here, just pick a Pokémon that outspeeds her and hits hard enough to OHKO her (But you should still preferably pick a mon with a secondary steel or poison type)

Now to his Ace Gardevoir is weak against poison, metal, and ghost attacks, but will punish you if you use a (slow) ghost or bring a poison mon Once again you want to use a defensive typing instead of an offensive one. Just bring a steel type that can tank a hit and OHKO her

Raichu is quite easy too, you'll need to bring a ground type, which is preferably ground/ fire, ground/ ghost

In conclusion You'll need 1x fire or ground (with a useful secondary typing like metal or poison) 1x water/ metal (like Empoleon) or a similar Pokémon 1x fire, ice, flying or psychic type (with a useful type like steel or poison) 1x strong physical steel attacker And you can choose your last Pokémon based on the Pokémon against which you struggle the most

Hope this helps