Empowered Orange Ambessa "I can't be dealt damages unless I am in combat" and Akali (Green) does "dodge" Uncheck power damages?

No to Akali, yes to Ambessa — depending on whether she's actually in combat.

Akali, Silent (Green/Calm): She takes the full 12. Unchecked Power says "deal 12 to ALL units at battlefields" — it never chooses or targets a unit, so her "can't be chosen by enemy spells and abilities" doesn't apply (Rules 756–757). This matches the existing ruling that Unchecked Power doesn't target, so even Deflect isn't owed (FAQ 7052). Untargetability only blocks effects that pick a unit out — a blanket "all units" effect gets through.

Empowered Ambessa, The Wolf: She survives the 12 as long as she is not in combat. While Empowered she has "can't be dealt damage unless I'm in combat," and "can't" beats the spell's "deal" (Rule 54). She's only "in combat" during a Combat Showdown where she's gained the Attacker/Defender designation (Rule 464.2.c.3; FAQ 11816) — a Non-Combat Showdown or just sitting at a battlefield doesn't count. If a Combat Showdown is genuinely ongoing at her battlefield, the 12 hits her and kills her (7 Might, 12 damage).

So the dodge belongs to Ambessa, not Akali.