Advice on sixth team member

So, I’m in Helios City, and I’m struggling to figure out my sixth team slot, for the in-game campaign. I got my butt kicked by Damian a few times before beating him before Helios, so I think I need to improve some things. I have:

  • Delta Venusaur (Calm Mind, Moonlight, Psychic, will have Moonblast)
  • Azumarill (Aqua Jet, Aqua Tail, Play Rough, will probably have Superpower)
  • Blaziken (Fire Punch, High Jump Kick (with Wide Lens), Swords Dance, Baton Pass)
  • Delta Gardevoir (Ice Beam, Thunderbolt, Moonblast (to be replaced with Earth Power when move tutor available), either Calm Mind or Livewire)

I like those four. For my fifth slot, I just decided to replace my Delta Muk with a Mega Flygon, which I’m excited about.

What I need help on is the sixth slot. I’ve been using a Haunter (about to evolve to Gengar in Helios), but I’ve been really underwhelmed. In theory, it is my fairy and ghost killer, but it is such a glass cannon that it gets killed if it doesn’t get a OHKO, and it just isn’t powerful enough (yet, at least) to get those OHKOs. It also gets killed by Dark moves on lots of different pokemon, especially Sucker Punch. It was useless against Damian’s Delta Charizard. (Maybe I’m just not using it right; I’ve not used it in previous pokemon games.)

What’s a better use of that sixth slot? I’d love to get a fairy killer (so maybe steel or poison), but the team seems to have a few other weaknesses, so I’m not sure whether fairy is the priority. Also, I’d love to get something that can set entry hazards, especially livewire – D. Gardevoir isn’t all that suited to the role. I’m not sure all of my team needs can be met by one pokemon. I’d love any suggestions you all had.

I’d probably go with another physical attacker, simply so you can get more options when baton passing your Blaziken, as the only one on your team that benefits from a BP’d swords dance is Azumarill.

Sorry I’m not here to answer your question, but can I borrow your delta muk for a bit? I need to finish my pokedex and I accidentally fainted mine while catching it.