Best with attacks that deal their damage to multiple targets: Dive Bomb is the prime example, but other good cases like Melee and Ricochet Beam exist.

Note that this increases damage of one attack. Things that are explicitly multiple attacks, such as Dance of Death or Slice and Dice do not synergize well with this.

On paper this card gives you 3 damage, spread out across three separate attacks, for 3ER. 3 damage for 3ER isn't too amazing, but I think there's real value in allowing you to assign damage more efficiently. For example, you can spend a use to get an extra card out of No Quarter or to one-shot one of the Sinister Six with Relentless Assault.

Can this effect be use with domino's pistols so it can make 2 damages for each resources? And where can I find the specific on when It would be valid and when it wouldn't

As others have pointed out this card works best at amping damage from a single attack with multiple targets. Some examples are given in the other reviews but my favorite is Wasp Giant form. Her basic attacks can be split between enemies by default resulting in each enemy taking additional damage. The ceiling for this can be incredibly high depending on scenario/player count (the more minions the better). This gets particularly fun when combined with Hand Cannon, Rapid Growth, and Follow Through for multiple instances of Overkill damage dumped onto the Villain. This particular combo is niche since it only works with Wasp, but she’s probably the most consistent user of this card.