You are fully capable of pulling these off with your armies. Mostly denoted when the end-of-battle statistics pop up with the words "HEROIC VICTORY" splayed across the top.
Very possible to capture a castle and defend it the very next turn against an army two or three times the size of your defenders simply through smart placement and movement of defending units. It's also extremely satisfying.
On top of all that, starting from Rome: Total War, your generals' exploits will become the stuff of legends in-universe. Your general will gain a reputation (and requisite stat-boosting trait) of Four-Star Badass, and for the rest of your campaign there will be a monument on the campaign map dedicated to your victory.