Baldur's Gate 3

There are any number of combinations of effects to do this, but what I'm listing below is the easiest, since it requires the fewest additional features and doesn't burn any resources like potions. All it requires is a level 5 fighter and two weapons that are both light and finesse (daggers, short swords, or hand crossbows.)

Basically you're just combining two fighter abilities: Extra Attack and Acction Surge, with dual-wielding.

So you can go....
- Bonus Action Off-Hand Attack
- Main Action attack
- Second attack
- Action Surge (get another action)
- Main action attack
- Second attack

There you go, five attacks in one turn, with no potions or anything burned, no complicated multi-classing, nothing.... just a fighter being a fighter.

A quick way of getting this would be a martial/melee class, such as Barbarian or Monk, combined with an Elixir of Speed and Extra Attack. Pop the elixir to be able to strike twice in one turn, but doubled with Extra Attack, it'll give you four; combine that with Monk gaining Unarmed Strike as a Bonus, or any other Bonus attacks as other melee classes, and you should get this starting:

Barbarian, Fighter, Monk, Paladin, and Ranger at level 5
Bard, using the College of Valour or Swords, at level 6

Fighter also acquires Improved Extra Attack, increasing the amount of additional attacks you can do from one to two, at level 11, so don't feel like you have to solely play Monk to get this trophy.