The ATCU (Advanced Threat Containment Unit) emerged in Season 3 as a potential threat to S.H.I.E.L.D. Though the two organisations shared an interest in Inhumans, it was clear that their strategies were completely different. They had a mysterious and charismatic leader and seemed ready to mess with S.H.I.E.L.D's plans. Only 4 episodes in, they feel mostly neutralised. Sure, they're going in guns blazing more than Coulson would like and Daisy doesn't trust them (though Daisy's judgement isn't worth much). But they're happily working alongside S.H.I.E.L.D. agents and the two leaders are making flirty eyes at each other and it's all generally a bit dull. Possibly (hopefully) the relationship will combust into something much more interesting. But until then, it'll just be scene after scene of meaningful glances and men in fatigues.