From what conditions can captains come back and ambush you?

Solution 1:

Orcs in this game are definitely persistent, that's for sure. As for how to guarantee they won't come back to gut you, it seems that in this sequel, there's very little to guarantee they won't come back.

This Kotaku Post covered the system in the prequel, Shadow of Mordor, and identified that not even decapitation (or lobotomy) ensured an Orc's demise, as the dev's had said:

Me: Regarding the nemesis system, do orcs only change their appearance/dialogue but still reappear if they SURVIVE a fight but still lose? Or do they ever come back to life (so to speak) to fight again the same way Talion does? I have one orc that I thought I killed but he's showed up to challenge me a few times since then, so I want to check if that's actually a possibility.

Monolith: If an Orc is not decapitated he can be scarred but cheat death and return to face you again. He should acknowledge this in his Showdowns and VO. This isn't like Talion where it is supernatural, it is just a result of them being extremely tough. You can decapitate a Captain by either

• Using a Chord (Triangle + Circle) when your Hit Counter is charged or
• Dominating him and selecting "Kill"

But, through testing, this has been proven to also not work. That being said however, there is one way to tell that an Orc is dead:

[...] there's a way to check whether or not an orc is likely to get back up off the ground. As the USGamer article points out, the best way to keep track of this is to go into the game's nemesis board after defeating an orc and see what their slot looks like in the aftermath of the fight. If the relevant orc is just lying there, there's a good chance he's not dead yet. If there's a little pile of skull and bones, on the other hand, you can rest assured that the guy's not coming back.

In Shadow of War, this "feature" seems to have been reinforced by the introduction of the "Cheating Death" feature, even in-so-far as to sport a ring-like scar around their neck, if previously decapitated.

However, as you see the body of the Orc on Army Screen, as long as the body does not disappear, that Orc or Olog has a chance to reappear and seek you out in combat again.

Again, the only hard indicator that an Orc is well and truly dead dead, not just pretending, is that they will appear as a small pile of skulls and bones on the Nemesis/Army board.

So, to answer your question: there is no, nor does there appear to be any particular "status" to ensure that an Orc is dead after defeat (either by betrayal or just general sport); only identifying whether or not they are dead.