Having 2 shitty characters doesn't makes everyone else look better, it just makes the story look worse.
This couple should have died on the flashback along with the sniper girl.
Edit: and for the people that don't get why these 2 are so horrible, they are sadist killers whose only joy is to kill and fuck, Nightmare's power is to control others and use them as meat-shields, she brainwashed an harem just to kill them, and her hobby is killing women she doesn't likes which includes every women except herself, she is narcissist that sees everyone as garbage, while the guy is just an adrenaline junkie that gets his kick from battle, as well as a womanizer, but at least he didn't go around killing the women he dated, unlike Nightmare.
Sniper Girl by comparison is the one that was just doing her work, and yet she died while these 2 assholes come back.