Foe Yay that Develops into a Relationship

So two of my characters happen to be rivals, they have very different opinions about things but they do have some hints at Unresolved Sexual Tension. Eventually they realize they're Not Too Different in some respects and slowly form a friendship which eventually develops into a romantic relationship.

I'm looking for tips/things to avoid to pull this off believably, as I've seen it done badly.

Here's an idea: Make them the Interservice Rivalry enemies, not "opposite sides" enemies. The antagonistic lovers have both the bitterness that comes from bad blood between their organizations, and initially won't together, but it doesn't raise alarms when that begins to change. It's also the more realistic way for them to carry on a relationship, since they can actually talk off the battlefield.

What rises must fall, what falls may rise again.

Actually they're on the same side and are forced to work together. They're not 'enemies' persay, they just initially don't like eahcother very much

That sounds more like Belligerent Sexual Tension than actual Foe Yay, then.

Fear is a superpower.

Yeah, I guess so... But should I add any 'hints' of Unresolved Sexual Tension BEFORE they manage to start befriending each other so it doesn't come out of nowhere?

I think that might help, yeah. Maybe acknowledge that they find one another attractive, even with a simple offhand line or two.

Fear is a superpower.