In 5e after level 5 a lone fighter can kill 4 goblins in one turn with a longbow and a use of action surge.
Seriously? Is not 3? OHK one, then another then use the action and another.
Action surge gives you another action. Extra attack gives you two attacks per action. So with your normal action, you kill 2 goblins. Then you action surge giving you another 2 attacks.
