There's been a lot of complaints about how obvious and telegraphed the final twist of Covenant was. When I think about the very first original Alien kinda had a similair twist with Ash. Similair in a way that how much it's obvious that something is up with the Nostromo's science office. There's a lot of signs - Ash preventing Ripley from going after the trio that went investigating Derelict, later letting them in against her orders, showing exceptional interest in creature's biology, protesting against terminating facehugger's corpse, whole scene with Ripley, stoping Parker from killing chestburster there and then, general coldness and emotionlessness etc. The difference is that even if you can suspect that Ash is up to no good, tries to protect Alien and will probably turn on his crewmates you still don't expect that he's gonna turn out to be a freaking robot that bleeds milk. In other words, you can pick up on the signs, you can expect a twist, it's pretty well telegraphed but you can't guess what the nature of a twist gonna be
