Exploring that tension is tricky because their canon dynamic is built on a foundation of trauma and a very slow, hard-won trust. A lot of fics I've seen stumble by rushing past the massive elephant in the room: he literally crucified her. The good ones don't ignore that; they use it as the central knot. The romantic tension isn't in sweet nothings, it's in the jagged edges of healing. Maybe it's Gajeel being hyper-aware of her personal space, forcing himself to back off even when she initiates contact, because he doesn't trust his own past instincts. Maybe it's Levy having a flashback mid-argument and the fight instantly draining from him, replaced by a cold, sick dread. The 'lemon' part, when it happens, often carries that weight—clumsy, charged with too much history, where passion is intertwined with apology and forgiveness spoken through actions, not words. It's less about steam and more about two people navigating a minefield of their own making, where every touch is a question and every surrender an answer.
I find the fics that focus on their mutual stubbornness work best. Levy isn't a passive victim; she's fiercely intelligent and holds a grudge. Her choosing to trust him again is an active, daily decision. The tension simmers in their bickering, which evolves from hostile to fondly exasperated, in the way he begrudgingly respects her mind, and in how she slowly uncovers the vulnerability he hides beneath all the iron and spikes.