If my opponent plays Cull the Weak with Repeat and I only have a single unit with a Guardian Angel equipped, does the unit die?

Ruling: Yes, your unit will die. Cull the Weak with Repeat creates two separate instances of "Each player kills one of their units." The first instance triggers Guardian Angel's replacement effect, which kills the Guardian Angel instead, then heals, exhausts, and recalls your unit to your base. However, when the second instance resolves, your unit is still a valid target because Cull the Weak does not restrict the kill instruction to units at a battlefield—units at your base are still on the board and can be chosen. Since Guardian Angel was already destroyed by the first instance, your unit must be killed by the second instance.

Sequence:

• First instance resolves: Guardian Angel replacement effect triggers, Guardian Angel is killed, unit is healed/exhausted/recalled to base
• Second instance resolves: You must choose a unit to kill; your unit at base is still a valid choice and dies

Nuances:

• Guardian Angel is a one-time use replacement effect that is destroyed when it saves the unit
• Units at your base are still "on the board" and can be targeted by effects that don't specify battlefield location