You cannot declare the Tyrant ambition.
In scoring, when you win any ambition, you only gain Power for second place. When returning Captives, you keep 1 Captive for each Bunker on the map.
Act: 3
A: No.
A: You gain Power for second place alone.
A: For scoring purpose, you did not win the ambition, so you gain the same power as the other Commonwealth members.