Hi! Interesting team composition. You have a lot of underrated pokemon on your team such as Conkeldurr and Mandibuzz that you don't see often in OU. The big problem with this team is that it's weak to a bunch of powerful offensive pokemon and at the same time can't break through certain defensive pokemon. This means that many of the games you play are going to be poor matchups since there are so many threats that the team has little to no answers to, many of these threats being pokemon such as Keldeo and Tornadus-Therian that are very common in the metagame. I know you in your post, you were only asking for a 6th pokemon for the team, but I don't think there's any pokemon that you can put onto the team that'll take care of enough of the team's problems to the point where they're manageable. Because of this, I'm going to be suggesting some changes that can be made to the team to improve it.
For starters, I think the idea of a fighting spam core is an interesting idea and I've seen it work before, but I don't think it's having much use on this team. Mega Lopunny is fine on the team, but I think Conkeldurr should be replaced with Latias.
Latias (F) @ Life Orb
Ability: Levitate
EVs: 72 HP / 184 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Draco Meteor
- Psyshock
- Defog
- Healing Wish
Latias is a bulky pokemon on the special side, much like AV Conkeldurr; however, Latias can take on a number of pokemon that the team doesn't have an answer to, such as Keldeo, Mega Charizard Y, and Mega Venusaur. Also, having Healing Wish to bring Mega Lopunny back to full health and remove a status infliction is a nice benefit to have on the team, as is hazard removal.
I wanted to find a way to keep CB Scizor on the team, but the team lacks a hazard setter which is vital for any competitive team to have and I couldn't think of a way to keep CB Scizor and add a hazard setter that could deal with the remaining threats--namely Starmie, Mega Heracross, and Mega Sableye. Because of this, I think that replacing Scizor with Hippowdon is the best choice.
Hippowdon (M) @ Leftovers
Ability: Sand Stream
EVs: 252 HP / 144 Def / 112 SpD
Impish Nature
- Stealth Rock
- Earthquake
- Toxic
- Slack Off
Unfortunately, the team loses some power by changing an offensive pokemon to a defensive one, but I think it's better for the team so that the team has a switch-in to pokemon like Magnezone, Mega Lopunny, Tornadus-Therian, and Terrakion--all of which could be a problem, with Mega Lopunny being a major threat. Having Hippowdon on the team also means that the team gets its much-needed hazard setter.
The team still has issues such as Mega Altaria, Starmie, Mega Sableye, Mega Heracross, and Weavile. The team also doesn't have anything to break through stall. Because of this, I suggest adding Clefable for the 6th pokemon because it can take on all of those threats as well as set up with Calm Mind to win against stall teams.
Clefable (M) @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 172 Def / 84 SpD
Calm Nature
IVs: 0 Atk
- Calm Mind
- Moonblast
- Thunder Wave
- Soft-Boiled
Finally, I think some of the sets need to be changed for the remaining pokemon.
First of all, I would change Drain Punch and Power-Up Punch on Mega Lopunny for High Jump Kick and Fake Out. Fake Out is something that I think is highly important to have on Mega Lopunny because it guarantees a safe mega evolution without being forced to switch out because of offensive pokemon that are faster than Lopunny's 339 speed prior to mega evolving. I think Ice Punch is more important than Power-Up Punch for this team because without Ice Punch, it's much harder to break through bulky ground types. High Jump should always be used over Drain Punch because even though the drawback from missing is pretty bad, the drop in power from Drain Punch compared to High Jump Kick is much worse overall.
Lastly, for Mandibuzz, I suggest changing the EV spread to 248 HP / 136 Def / 108 SpD / 16 Spe. This spread makes Mandibuzz faster than max speed Adamant Azumarill which allows Mandibuzz to outspeed it and hit it with a Foul Play. The SpD EVs allows it to avoid the 2HKO from Gengar's Sludge Wave at full health if Stealth Rock isn't up, and the rest of the EVs go into HP and Defense for bulk. Also, I suggest running Taunt over Defog and possibly Knock Off over Whirlwind. Since Latias is the new defogger, Mandibuzz doesn't need it anymore. I think Knock Off might be better than Whirlwind for this team because there's no other pokemon that has Knock Off on the team and getting rid of items can be pretty beneficial.
I realize that the team shifted towards a balance team from what appeared to be a bulky offense team in the original post, so I apologize if balance isn't what you want out of this team. As a final word of advice, be extremely cautious with this team when playing against Mega Gyarados teams because it pretty much 6-0's the team if it sets up. Your only hope against it if it gets to +1 is to have Mega Lopunny at full health, hope that Mega Gyarados doesn't get a lucky roll to OHKO Lopunny (18.8% chance to OHKO), and hit the High Jump Kick to take it out (and on a minor note, hope that Gyarados is mega evolved in the first place so that Mega Lopunny can actually beat it).
Good luck with the new team!
Summary of Changes
>
>
for 6th pokemon
HJK>Drain Punch, Fake Out>PuP
Taunt>Defog, Knock Off>Whirlwind
Importable
Lopunny (M) @ Lopunnite
Ability: Limber
Happiness: 0
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Fake Out
- High Jump Kick
- Frustration
- Ice Punch
Magnezone @ Choice Scarf
Ability: Magnet Pull
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Thunderbolt
- Hidden Power [Fire]
- Flash Cannon
- Volt Switch
Mandibuzz @ Leftovers
Ability: Overcoat
EVs: 248 HP / 136 Def / 108 SpD / 16 Spe
Bold Nature
- Foul Play
- Roost
- Taunt
- Knock Off
Latias @ Life Orb
Ability: Levitate
EVs: 72 HP / 184 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Draco Meteor
- Psyshock
- Defog
- Healing Wish
Hippowdon (M) @ Leftovers
Ability: Sand Stream
EVs: 252 HP / 144 Def / 112 SpD
Impish Nature
- Stealth Rock
- Earthquake
- Toxic
- Slack Off
Clefable (M) @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 172 Def / 84 SpD
Calm Nature
IVs: 0 Atk
- Calm Mind
- Moonblast
- Thunder Wave
- Soft-Boiled