Rate my OU team, mates :)

[Udders]

Banette (F) @ Banettite
Trait: Cursed Body
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Destiny Bond
- Gunk Shot
- Shadow Claw
- Sucker Punch

Tyranitar (F) @ Leftovers
Trait: Sand Stream
EVs: 252 HP / 252 Atk / 4 Def
Adamant Nature (+Atk, -SAtk)
- Stealth Rock
- Crunch
- Counter
- Stone Edge

Icy King (Kyurem-B) @ Life Orb
Shiny: Yes
Trait: Teravolt
EVs: 56 HP / 252 SAtk / 200 Spd
Mild Nature (+SAtk, -Def)
- Dragon Pulse
- Fusion Bolt
- Ice Beam
- Earth Power

Volcarona (F) @ Life Orb
Trait: Flame Body
EVs: 252 SAtk / 4 SDef / 252 Spd
Timid Nature (+Spd, -Atk)
- Quiver Dance
- Fire Blast
- Giga Drain
- Bug Buzz

Sylveon (F) @ Choice Specs
Trait: Pixilate
EVs: 252 HP / 252 SAtk / 4 SDef
IVs: 30 Atk / 30 SAtk / 30 Spd
Modest Nature (+SAtk, -Atk)
- Hyper Voice
- Hidden Power [Fire]
- Shadow Ball
- Psyshock

Gyarados (M) @ Leftovers
Trait: Intimidate
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Dragon Dance
- Waterfall
- Bounce
- Earthquake


That's the team. I haven't really put much thought into it I just chose Pokemon I like and I think they are gonna do a good job in there. Like, I have my DD Gyarados for sweeping, Volcarona for the special sweep, Kyurem is a great Wallbreaker, Sylveon is the best fairy and I opted for an offensive set that I always wanted to try out. Banette is a pure charm! It's one of my favorite megas that's why I'm using it. It's very good too. Tyranitar has nice coverage with Banette. It's my leader and he just sets up rocks and then goes on or dies after countering a physical attack.

So is it good?

 

[PlatinumDude]

While Mega Banette has strong offensive presence, it's outclassed by Mega Sableye, due to its better bulk:
-Calm Mind
-Dark Pulse/Shadow Ball
-Will-o-Wisp
-Recover
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Sablenite
Ability: Prankster

Yes, Tyranitar has the physical bulk to bounce physical hits back with Counter, but it's not worth using because it takes up a valuable coverage moveslot. Skarmory is a better Counter user because of its fewer weaknesses and better defensive typing. It also provides crucial Defog support if you're interested in that (as Volcarona and Black Kyurem are weak to Stealth Rock), while bulky Excadrill can set up Stealth Rock and provide Rapid Spin support at once:
-Brave Bird/Counter
-Spikes/Stealth Rock/Defog
-Whirlwind/Taunt
-Roost
Nature: Impish/Bold
EVs: 248 HP/252 Def/8 SDef
Item: Leftovers/Rocky Helmet
Ability: Sturdy

or
-Iron Head
-Spikes/Stealth Rock
-Whirlwind/Taunt
-Roost
Nature: Careful
EVs: 248 HP/8 Def/252 SDef
Item: Leftovers
Ability: Sturdy

Excadrill:
-Earthquake
-Iron Head
-Rapid Spin
-Stealth Rock
Nature: Careful
EVs: 252 HP/4 Atk/252 SDef
Item: Leftovers
Ability: Mold Breaker

Sylveon benefits more from Baton Pass than Shadow Ball or Hidden Power. Sure, it seems pointless without stat-boosting moves, but Sylveon's Baton Pass is in a lower priority bracket than dry switching. Because of its low Speed, Sylveon can tank a hit, then Baton Pass away to a teammate to get it into battle safely.

The only Dragon move worth considering on Black Kyurem is Outrage to hit special walls harder than Fusion Bolt would. Ice Beam already provides a special STAB:
-Outrage/Roost
-Ice Beam
-Fusion Bolt
-Earth Power
Nature: Mild
EVs: 20 Atk/252 SAtk/236 Spe
Item: Life Orb

or
-Substitute
-Ice Beam
-Fusion Bolt
-Earth Power/Roost
Nature: Mild
EVs: 56 HP/216 SAtk/232 Spe
Item: Leftovers

or
-Outrage
-Ice Beam
-Fusion Bolt
-Dragon Claw/Iron Head
Nature: Naive
EVs: 252 Atk/32 SAtk/224 Spe
Item: Choice Scarf

Dragon Dance vanilla Gyarados faces stiff competition from its Mega counterpart because the latter has better bulk to get Dragon Dances off more easily. Feraligatr happens to hit harder thanks to Sheer Force:
-Dragon Dance
-Waterfall
-Superpower/Ice Punch
-Crunch/Ice Punch
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb
Ability: Sheer Force