The following characters negate Hirudegarn's skill which reduces damage taken and deal more damage to Hirudegarn. Only SSR or above characters are listed here.
You'll get 2x Master Roshi (Santa Claus) from each multi summon. This character is used to increase Super ATK lvl 100%.
The following cards can be LR by Dokkan Awaken but the summon rate for them are not increased.
Dokkan Battle Reroll Tier List
Blazing Blue Fusion
[Full Force Power] Vegito
Day of Destiny Super Saiyan Gohan (Youth)
[Mixed Feelings] Vegeta