Brutal Combat (Overkill Supplement)
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Combat fun is all about the mayhem, the visceral thrill, and the fatality. In those respects, the D&D rules fall flat for simulating a good combat campaign, because the vanilla rules simply are not METAL enough. In that respect I propose the following collection of alternatives and options which you can use to enhance your campaign.
Grappling and Wrestling
For a general reference: See the relevant SRD page.
The following rules make grappling more fun, more effective, and more meaningful.
On your turn, you may use your action to brace a creature that you are grappling, leaving it exposed and defenseless against blunt trauma (e.g. so that your friends can all wail on it). When you do so, the creature takes double damage from all bludgeoning damage until the start of your next turn.
Sometimes you just want to lay your hands on someone's scrawny little throat and choke the living daylights out of them. To do that, first you must have established a successful neck grab. Next, you must use your action to make another grapple check. On a success, the creature you are grappling is now choking and will fall unconscious in a matter of seconds. When you reduce a creature to 0 hit points by choking it, you may choose to knock it out instead of killing it, leaving it unconscious but stable as usual.
When you grapple a creature, you are assumed to be grabbing it by the body or by one of its limbs. By making your initial grapple check at disadvantage, you may choose to grab a creature by its throat instead. This has no immediate benefit, but it does unlock some very cruel combat options.
Pinning a Creature
You can use your action to pin a creature that you're grappling. Make a grapple check. On a success, both you and the creature you're grappling are restrained for the duration of the grapple.
You can use the Attack action to throw a creature that you're grappling, provided you are strong enough to lift it. A throw can represent a number of different throws, from a deft Judo throw to simply lifting a dude over your head and hurling him skull-first into the ground like a javelin. If you're able to make multiple attacks with the Attack action, this attack replaces one of them. A thrown creature takes bludgeoning damage equal to twice the damage die of your unarmed strike, and lands prone in a space within 5 feet of you. You can throw a creature into a space occupied by another creature. If you do, the creature in that space must succeed on a Dexterity saving throw or take the same amount of damage and be knocked prone if it is no larger than the same size category as the thrown creature.
Wrenching Limbs and Snapping Necks
You can use your action to wrench the arm or leg of a creature that you're grappling. Make a grapple check. On a success, the grappled creature takes bludgeoning damage equal to twice the damage die of your unarmed strike, and it must make a Strength saving throw (DC = 8 + your Strength modifier + your proficiency bonus). On a failure, one of that creature's limbs is crippled.
If you have established a successful neck grab, you may choose to try and snap a creature's neck, which works on the same principles but is significantly more lethal. On a successful grapple check, the grappled creature takes bludgeoning damage equal to four times the damage die of your unarmed strike.
Jumping and Flying Attacks
You may declare the first attack you make on your turn to be jump attack. If you hit a creature with a jump attack, your attack deals an additional 1d6 damage. However, if you miss with a jump attack, you will look quite foolish, fall to the ground prone, and you may not take any actions or bonus actions until the start of your next turn.
If that's not risky enough for you, you may be interested in the flying jump attack, a very showy high-power move which carries a lot more risk with it. If you use the dash action and during your movement move at least 15 feet in a straight line, you may use your bonus action to make a flying jump attack. If you hit a creature with a jump attack, your attack deals double your weapon's damage dice in damage, plus 10 additional points of damage. However, if you miss with a flying jump attack, you take 1d6 points of falling damage, you fall to the ground prone, and you are stunned until the end of your next turn.