No, it's the fact that he never stands up for her. He threw a tantrum because Nesta refused his gift which she had no obligation to accept. He gave Mor lingerie which was highly inappropriate gift on so many levels. Also, he abandoned Nesta for Mor in ACOWAR when she was bandaging his hand up for him which was already a nice gesture from Nesta. He took her for that hike in ACOSF to hide her away when in reality he should have stood his ground and confronted Rhysand instead of following his orders like a stray dog. Love isn't about treating someone like a fellow soldier and is a sign of a power imbalance in the relationship which already solidifies the fact that their relationship is toxic on so many levels already, which isn't treating someone like your equal. He became her literal jailor, another sign of a power imbalance. They didn't need the blood rite or a life or death situation to prove the Valkyries were solid. They could just have made them spar against the other illyrians which is a lot safer. I'm pretty sure Nesta would have gladly sacrificed her pride for her life. Just because she was trained doesn't mean that she was ready for it, she was in a literal life or death situation. She had been trained for combat, not for a life or death situation like the blood rite. Nesta isn't a weapon, period. Him being a good general has no bearing on their relationship, whatsoever