Battle Moveset

A Good Moveset for Kingdra would have to be this:

Attacks:

Surf
Rain Dance
Ice Beam
Rest/Dragonbreath/Hidden Power [Electric]

Items Attached:

Leftovers

Preferred Nature:

Modest

Strategy Using Kingdra

Kingdra. well, it's overrated. Special Walls and Water types just basically make Kingdra cringe and its move pool is just the generic Water move pool, nothing particularly special that it can use effectively.

The Dragon duel type may look like its an advantage, but when it comes to Kingdra vs. Generic Water type, you'll learn to hate it. The duel Dragon type means your opponent can freely Ice Beam you while you're stuck with a "Not Very Effective" set of moves. Hidden Power [Electric] will do 'meh' damage to most Water typed opponents but it's the best you've got one on one. Personally, I'd say go with Rest, since that way you can at least beat Blissey one on one (stall it out of Seismic Tosses).

Anyway, we all know the strategy. Rain Dance doubles speed and boosts Surf, which will then go ahead and destroy everything that doesn't resist so long as isn't called Blissey/Regice/Snorlax (there are a few others but I can't think of them off the top of my head). In the Uber Metagame, ditch Rain Dance and replace it for one of the last slot moves, since you'll probably face/have a Kyogre.

EV Corner:

EVs: 244 HP / 14 Def / 252 SAtk
Modest Nature (+SAtk, -Atk)

Max Leftovers Recovery and Max Special Attack.

EVs: 40 HP / 218 Def / 252 SAtk
Modest Nature (+SAtk, -Atk)

A lot of Defence on this one since Kingdra joins the rest of the Water Pokémon in being a sweet switch in on Metagross. There's a lot more physically based threats than special based ones anyway and Kingdra draws in Snorlaxes very effectively.

EVs: 40 HP / / 252 SAtk / 218 SDef
Modest Nature (+SAtk, -Atk)

Same as above except this one has SDef > Def. It'll help against Regice and will absorb Ice Beams better from other Water types but that's pretty much it.

Other Optional Sets:

Kingdra @ Liechi Berry or Leftovers
Trait: Swift Swim
EVs: 40 HP / 252 Atk / 60 Spd / 158 SAtk
Brave Nature (+Atk, -Spd)
- Flail or Return or Mimic
- Dragon Dance
- Hidden Power [Ghost or Rock or Ground] or Substitute or Endure
- Hydro Pump or Substitute or Endure

The sad truth is Kingdra needs 2 Dragon Dances to even come close to being a threat physically. You can usually kick one off freely anyway, since the standard switch-in on Kingdra is a special sponge. Un-STABed Flail isn't too hot so I'd just say go with Return, since Flail needs the support of Substitute/Endure to become useful and with Tyranitar's Sandstorm running around, you might encounter some problems anyway. Hydro Pump blasts away Skarmorys, Steelixes, Tyranitars and other critters who give physical attackers problems. Hidden Power gets whatever it can depending on its type. We all know how Mimic works and it could pay off, since nabbing an Earthquake could be crucial when you consider Kingdra's poor excuse for a move pool.

Strategy Against Kingdra

I know you're expecting me to give mention to Dragon attacks. but I'd like to know what the hell uses them? Almost all Dragon types are Dragon Dancers/Choice Banders and shouldn't have Dragon Claw while the special sweepers have move pools so wide that Dragon Claw is a waste of space. If you have a Dragon attack, use it, but you better have a damn good reason for wasting a move slot on it, otherwise the rest of the Kingdra's team will abuse you.

The Swift-Swim-Sweeper: That Dragon-duel will have your little Water types dancing up and down, since they can freely switch into Kingdra and Ice Beam it away. Blisseys, Snorlaxes, Regices and other Special Sponges also get to party on Kingdra, experiencing "free-set-up-time" to do whatever they please. Swift Swimmers should begin rejoicing since Kingdra has set them up as well as anything else that gets a benefit from Rain Dance. You really don't "counter" Kingdra but rather make it run away/waste its PP. It kinda just sits there until there's nothing left to take out, since-to its credit-it doesn't get owned directly by anything unboosted.

The Dragon Dancer: Chances are you gave it a free Dragon Dance. Never fear, even with only one Dragon Dance under its belt the limited move pool will haunt it. Try to avoid switching in a physical wall since most of them will get dented by an inevitable Hydro Pump. Just use things that can take physical hits to beat it. Lack of STAB and move pool basically mean it isn't something to be feared until it gets 2 or 3 Dragon Dances under its belt. Physically defensive water types are your best bet (along the lines of Suicune, Blastoise and to a lesser extent, Starmie), although anything physically defensive (that doesn't take a super effective from Hydro Pump and has passable Special Defence - a.k.a not Skarmory) should be usable.

Kingdra is basically:
- A poor water type.
- A sub-par special sweeper.
- A sub-par sponge.
- The worst fully-evolved Dragon Dancer in the game (tied with Lapras).
- A waste of space.

It joins things like Moltres as being "Too useless for OU but too strong for UU" and gets left in the dark realm of the unused. Chances are the only time you'll come across this guy is when facing a newbie, so don't expect anything special from it.

Contest Moveset

A good Contest Moveset for Kingdra would have to be this for the Beauty Contest best with Modest, Mild, Rash or Quiet Nature:

Attacks:

Rain dance
Surf
Hail
Hyper beam

Items Attached:

Blue Scarf

Strategy Using Kingdra

If you do the attacks in this following order you should have very few problems; 1st - Rain dance, 2nd - Surf, 3rd - Rain dance, 4th - Surf/Hail, 5th - Hyper beam

Locations in Games

Ruby/Sapphire/Emerald Evolve Seadra Colosseum Trade from R/S/E/FR/LG Fire Red/Leaf Green Evolve Seadra

Animé Appearences

Kingdra has had a few Animé Appearences. First Molly Used one in her battle against Misty, Ash battled one in the Whirl Tournement and Clair used it in her battles against Ash Movie 3: Spell Of The Unown Episode 218: Dueling Heroes! Episode 254: Fangs For Nothin`! Episode 256: Better Eight Than Never!