Destructive Strength (5e Feat)
From D&D Wiki
Prerequisites: 1 Ability score at 20
You ready your might and put your all into your attacks, overexerting yourself to deal devastating damage. When you roll one or more damage dice, you can choose up to forgo rolling a number of those dice up to your highest ability score modifier (a minimum of one). Use the maximum value for those dice and roll the rest. You can't use this feature again until you finish a long rest.