S2:E15: Cease Fire: Captain Archer receives orders from Starfleet Command that his presence was requested to help to negotiate a cease fire between the Andorians & the Vulcans.
While battling the Vulcans in a territorial dispute, Commander Shran sends word through the Vulcan High Command, requesting the help of Captain Jonathan Archer to attempt to resolove this dispute. Upon receiving word of the request, Enterprise changes course to see how they can help.
Once contact is made with Commander Shran, Archer returns to Enterprise to escort Ambassador Soval down to the planet. Unfortunately, their shuttlepod comes under fire and are forced down in the middle of battle. It's here in this negotiations that Archer comes to the conclusion that maybe humanity was truly ready to become a bigger part of the interstellar community.
For me, the best interraction comes at the end of the episode when Ambassador Soval states, "Captain, your presence here has not been...overly meddlesome." To which, Shran comments, "I think he likes you, pink skin," which Captain Archer responds with, "I wouldn't go that far."
There are a number of other good episodes from Season 2 that were hard to keep off of this list, my honorable mentions include: "A Night In Sickbay", "Singularity", "Future Tense", "Cogenitor" & "First Flight"