Caitlyn, Patrolling

465.2.c.8. If a Unit has one or more Abilities or effects applying to it that demand it be assigned damage in a specific way that is exclusionary, then the assigning player chooses only one of those abilities to apply when assigning damage. Example: Caitlyn, Patrolling with the Backline ability ("I must be assigned combat damage last.") has been given the Tank ability ("I must be assigned combat damage first."). A player is assigning damage to this Caitlyn with Tank and two units with no abilities. That player can't fulfill both of Caitlyn's damage requirements, so they may choose to assign damage to Caitlyn first, fulfilling the Tank requirement, or last, fulfilling the Backline requirement. They can't choose to apply damage to Caitlyn in between the other two units, because that wouldn't fulfill either requirement.

465.2.c.9. If there is more than one unit in which this situation applies to, each unit is dealt with individually. The assigning player chooses which ability or effect applies, and then resolves the assignment. If this creates a situation where now more than one unit must be assigned with the same priority, those units may be assigned damage in any order as normal within that priority. Example: Two copies of Caitlyn, Patrolling with the Backline ability ("I must be assigned combat damage last.") have been given the Tank ability ("I must be assigned combat damage first."). A player assigning damage to these two Caitlyns and one unit with no abilities could choose to fulfill both Caitlyns' Tank requirements by assigning them both damage before the other unit.