I think there was always a Romulan Ambassador to the Federation, or in some sense, working with the Federation when it came to disputes that fell along the lines of the NZ and I was always under the impression that the Klingons and Romulans worked together or at least shared ideas since they had a common enemy which probably would be why the Romulan Ambassador was there in VI.
the comparison of Khan to Nero is wrong because Kirk really WAS an opponent of Khan's who was also responsible for his predicament in a way.(Both for leaving him there and not checking up on him and his group)
Spock was of course not an opponent of Nero's in any way, but was also actively trying to HELP the Romulans and was IN NO WAY RESPONSIBLE FOR NERO'S PREDICAMENT.
Bit of a difference there.
What? Kirk gave Khan pardon and stated that he'd give him a planet in which to reign. He agreed, that chick agreed, and they left on good terms. Spock then says something along the lines of it being interesting to visit the planet 100 years from now to see what came of the seed they planted. Kirk never agreed to check up on them nor was there any plans on visiting them again to make sure " they're doing okay ".
Khan
agreed to Kirk's proposal. He become insane when the planet he lived on suffered a
natural disaster and turned it into a wasteland that killed his wife and half his people. That was not Kirk's fault but Khan adamantly believed it
was just by association. So how does that then make Kirk an equal opponent?
Kirk helped Khan by feeding his ego. It backfired because he tried to come up with a half assed stupid solution for another no-win scenario.
Spock didn't have to say that he could save their planet. He didn't have to come up with some device to absorb the supernova but he did. He gave them hope and it backfired. Just like Kirk.
Two individuals misguided with resentment due to, what they feel as, false hope. It's the same approach, there is
no difference.