Lower Gameplay for Beat-Em-Up style game scene

I'm making a game scene with multiple enemies. The enemies are all exact copies each other, - same models, same animations, same logic - however the gameplay thermo boils rapidly when adding more of them. I want my character to be able to fight around 10-20 enemies at once, but lagging gets pretty bad at around 6, which is worrying since I haven't even finished creating the enemy logic nor even started the logic of the playable character.
1 enemy alone = 8% gameplay on the thermometer. However the scene experiences a lot of lag at just 60% gameplay. This is before I've even begun constructing the level (My scene currently only has a plane and a bunch of cloned enemies to run a test).

Are they any significant methods available to run these scripts without the lag issues? The scene I plan doesn't get much more complex, it's mostly just fighting enemies.