Hades has been put on a very tight leash by Sylens and though he is still an indirect threat by way of using him for knowledge or to use him to override machines but not on the level of Hephaestus. Hephaestus still has full reign to do what he does. Build machines and for him the deadlier the better. Given that hades threat level is proportional to Hephaestus’s threat level given that hades is only as dangerous as the machine Hephaestus creates and hades therefore corrupts. But Hephaestus has hades in that regard as daemons machines are stronger then even corrupted machines.
To sum it up hades is locked in a cage picking off Hephaestus’s scraps while Hephaestus is out here calling the shots and taking lives.