If i attack with an empowered Ambessa, Respected and Feared and in response to my when i attack, my opponent plays a Temporal Breach from hidden, can he blink my Ambessa, Respected and Feared and avoid its effect of killing a unit with less might?

Yes — the blink works. The kill doesn't happen, because Ambessa's "when I attack" trigger is already on the chain and its referents get re-checked when it resolves, not when it triggered.

The window exists because the attack trigger creates a Closed State, so only Reaction-speed responses are legal — Hidden gives Temporal Breach that. When the trigger resolves, "here" and "less Might than me" are referents checked on execution (Rule 359.3.f.2). After the Breach, Ambessa is a new game object (Rule 124.1) — she loses the Empowered status, so the dependent kill ability is no longer even active — and her position/status has changed, so that referent returns null and the kill instruction is ignored. This is the same pattern as the standing ruling that a pending trigger referencing a Breached unit does nothing (FAQ #12419).

Two caveats worth flagging: the hidden Breach must have been hidden at that battlefield (Rule 811.1.d.2) and on a previous turn, or it can't be played at all. And since you're the attacker, you don't control the battlefield you're attacking — so "its owner plays it to the same location" may be impossible, leaving Ambessa stuck in banishment rather than returning (same location problem as Arcane Shift; Rule 359.3.e.6, cf. FAQ #12422/#8609). Either way the enemy unit survives.

This is my interpretation on the "stuck in banishment" half — there's no official FAQ for Temporal Breach on an attacking unit, and it's worth a second look before you rely on it in a tournament.