Vengeance

Vengeance is an attack style characterized as a dynamic attack speed buff that changes upon losing or gaining lives. It is introduced in Bloons TD 6 with the introduction of Heart of Vengeance. It is part of the damage types family.

Vengeance is represented on the Bloons Wiki as, the upgrade icon for Heart of Vengeance in Bloons TD 6, since that is, currently, the only upgrade that does this. It is different from Retaliation in that Vengeance   can change how much lives the player currently has and that the effect is permanent (barring lives-restoring sources) rather than an ability that has a cooldown.

In this case, Vengeance gains a stronger attack speed buff, the more lives that are lost and a weaker (and maybe nonexistent) attack speed buff, the more lives that are regained. If there is any attack that does not increase or decrease the attack speed of a tower, depending on the number of lives the player has, then it should not be considered Vengeance.

All attacks require an upgrade in order to have Vengeance.