Mount & Blade II: Bannerlord

If you play the story campaign you should get this as part of the introduction to the game. You must have at least 10 troops to storm a hideout and you uncover them on the map before attacking them. The story intro guides your hand on this very well so I will not comment further on it.

If you have jumped straight into a sandbox campaign though, hideouts usually appear most when a nation is at war due to the civil unrest caused. You can get a general idea of where one is on the map due to the increasing volume of bandits you see roaming on the map. Your scouting skill comes in to play as well, but the closer you get to the hideout, the more chance it will appear on the map.

Once you find one, click it and wait for night to fall. Attack the camp with your 10 chosen troops and once load in, hold LB and then press the formation button and order your troops to charge, your troops will run ahead and attach the bandits, reducing their numbers to zero, at this point the bandit leader will appear with some men, throwing you in to a conversation where you can chose to beat him in a one-on-one duel or allow your troops to fight each other, it is up to you. So long as you win, the achievement should pop once you close the battle report.