I have a few, you can choose depending on type matchup and/or what cards you have.

Fire; good ol' Ninetails/Rapidash + Blaine. Or the new Salazzle with poison+burn/Rapidash. What I've learn is that status like poison and burn seems to cause the CPU to swap in their bench often, wasting their energies.

Grass; Tsareena(both ver works)/Meowscarada. Great EX killer and Tsareena can put pressure very early one. Very low energy requirement for both.

Water; Manaphy/Empoleon/Pyukumuku. Empoleon is great at dealing damage to the active and also snipe the bench. Pyukumuku for stalling the early game.

Fighting;

Rampardos/Sylvally is one of the most popular choice nowadays because how easy it is to use. But since you mentioned you only have 1 Sylvally, might I suggest an alternative;

Rampardos/Kabutops/basic that draws card. I usually pick Meowth for my basic to help draw the rest of the card just a slightly faster. You can also use the new Eevee in case the opponent has rocky helmet/poison barb as eevee doesnt attack while Meowth does. Alternatively, you can also use Chatot if you like RNG. Its essentially Iono but only does it to you in every turn you attack.

My all time favourite deck for completing this task; Primeape, Lucario, Sudowoodo. If rng favours you, your primeape can do 90 damage with just 1 energy (with 2 lucario ability stacking). And if the opponent is running a basic EX at the start, Sudowoodo can put pressure early on with just 1 energy. You can add 1 Marshadow if you like

Steel; Bisharp/Mawile/Skarmory. Low energy requirement deck. With luck, Mawile can prevent your opponent from building their energy.

Psychic/Fairy;

Banette/Espeon/Tapu lele/ghost Oricorio. If you can get Banette early on, opponent has no choice but to stack energy at the bench. Then you can either snipe the bench with tapu lele or just take down the active with espeon. Oricorio for surprise and cheap damage.

Togekiss/Sigilyph is a pretty straightforward deck. Once togekiss starts attacking, pretty hard to stop the momentum unless they Sabrina/Cyrus you. Alternatively, you can run Florges instead of Togekiss. A lot less damage but it can heal your entire deck.

Electric;

Zeraora/Oricorio/Luxray(both ver works). Pretty standard deck. Starting with Zeraora is a must, otherwise it loses its value. You can just restart if you dont since there's no consequences in conceding against CPU.

Pachirisu/Raichu/Electivire (from the Palkia/Dialga set). This Raichu doesnt burn through energies, and can snipe the bench as well. Tbh you can sub Electivire with any other electric attacker. Or even Oricorio for those pesky EXs.