FATEwiki - One-on-Many Combat

In a one-on-many combat exchange, the "one" still only rolls once. (FUG 44).

EXAMPLE: So if Bad Guys B1 and B2 are both attacking Good Guy G1, each of them rolls only once for the exchange (B1 and B2 also get the Superior Numbers advantage).

If any of the "many" side win the exchange, that's the side that wins. Each of the combatants who beat the lone combatant gets to inflict damage (based on the MoS in the Wounds Table).
EXAMPLE: G1 gets a Good, B1 gets a Great, and B2 gets a Fair. That means the Bad Guys win the exchange. Only B1 actually does damage, though, an MoS of 1 (Clipped).
If the lone combatant beats all the "many" side (even with only an MoS of 0):
- The lone combatant can inflict damage on one opponent, based on their MoS against that opponent (not necessarily the MoS that won the combat -- usually they choose the roller, to get the best MoS and worst damage). [1]
  EXAMPLE: G1 gets a Great result, vs the Great result of B1 and the Fair result of B2. G1 wins the exchange, and inflicts a Hurt (MoS of 3) on B2.
- The lone combatant can inflict damage on more than one of the opponents, based on their MoS on each; however, the damage inflicted is one Result Level less per additional target damaged (an Injury becomes a Hurt, a Hurt becomes a Clipped, a Clipped becomes a Scratch, etc.). [2]
  EXAMPLE: G1 gets a Legendary result, vs the Average result of B1 and the Good result of B2. G1 wins the exchange, and decides to inflict damage on both of them. Ordinarily that would be an MoS of 6 and 4, Injured and Hurt, but with two targets, that drops a level (each) to Hurt and Clipped. So the alternative is between Injuring one Bad Guy, or Hurting one and Clipping the other.

The exception to this allocation of damage can be found in Grenade Rules.

Combat Rules, Many-on-ManyCombat, ExchangeCombatExamples.

Landon Darkwood offered an alternative [3]

[...] If a dude with an SMG wants to shoot two dudes, he rolls in an exchange vs. both of them, but each of the two dudes takes a +1 for outnumbering SMG-dude. If SMG-dude beats both of them in the resulting rolls, the GM might rule that autofire allows him to damage them both, though the default rules state he can only damage one person per exchange in multiple-person combat. Additionally, if he gets beat by both people, he's going to take two damage effects - could be pretty nasty for him in the end.

[...] In my Hong Kong Action Theatre Fate game, I have a couple of "mook rules" that I use whenever the characters are fighting nameless thugs. They are:

(For more gritty, slow-paced HK action) If the PC is fighting a group of mooks, he can damage as many of the mooks as he beats in the exchange and it just gets narrated into the resolution of the exchange. So if he's fighting four guys and gets MoS on three of them, three of the thugs take the appropriate damage effect, and the PC takes the damage from the last thug that beat him. Normally, I don't give thugs outnumbering bonuses either, but that's GM discretion.

(For really over-the-top cinematics) A group of mooks gets statted as a single challenge grid and attacks as a single entity. Their numbers almost don't matter. As the PC gets boxes marked off on the mooks' challenge grid, they get narrated as dropping out of the combat. When the challenge grid is filled out, all the mooks are gone. In fact, if it's dramatically appropriate, the GM can continue narrating mooks into the scene as they take damage - the challenge grid is really only measuring, at this point, progress until the end of the scene. To parallel the normal damage grid, you can assign the mob -1 penalties as you go for losing people or just being damn scared of the mook-trashing PC.