YagamiLight
Smash Champion
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#350 Milotic
Typing: Water
Ability: Marvel Scale - Increases Defense by 50% if struck with a status move.
95/60/79/100/125/81
Instant Recovery
Milotic @ Leftovers
Marvel Scale/Bold
144 HP / 252 Def / 108 SpD
Recover
Hypnosis/ Toxic
Surf
Ice Beam/ Hidden Power Electric
The premise is simple as ever, Milotic is a standard high-class bulky Water. Milotic's goal is to use it's solid defenses and resistances to absorb damage and recover away the damage as they switch to another Pokemon. The instant heal move Recover and the ability Marvel scale are what make Milotic a unique and overall high quality choice for your team. By selectively hitting yourself with the right status, Milotic's physical defense goes from mediocre to outstanding. Hypnosis and Toxic are fairly standard status moves, use whichever one seems to appeal to you. Platinum brought around a hit percentage reduction for Hypnosis, so that might make the fairly consistent Toxic even more appealing. Surf is an obligatory status move which still packs a punch coming off 100 Base Special Attack. The last move is for coverage, if you'd like to stop dragons and grass Pokemon, go with Ice Beam. If you find a need to stop other water types, HP Electric will serve you well.
ReSTalker
Milotic @ Leftovers
Marvel Scale/Bold
252HP/240 Def/16 SpD
Rest
Sleep Talk
Surf
Ice Beam/Hidden Power Electric
The standard Rest and Sleep Talk set made even better by the automatic 50% defensive boost that Milotic incurs upon going to sleep. This set is far better off at status absorption than the previous set, but it loses the ability to hand out Status itself. The idea is still simple, come in on any attack, heal it off and continue to attack the team and force their hand by bombaring them with attacks. Surf makes a return here, as does the rather hard choice between Ice Beam and HP Electric. This should be used over the aforementioned set if your team is slower paced and wants to shore up more weaknesses.
Choice Milotic
Milotic @ Choice Scarf/Choice Specs
Marvel Scale/Timid
4HP/252 Sp Atk/ 252 Spd
Hydro Pump
Ice Beam
Hidden Power Electric
Dragon Pulse/Surf/Hypnosis
A bit of an odd route for a standard defensive Pokemon like Milotic, but definitely still a reasonable option. Milotic's excellent type coverage and well as 100 Sp Atk /81 Speed base stats make this set a reality. Hydro Pump simply hits hard with it's initial base power plus STAB. Boltbeam offers very little in the way of resists and the final move is basically for convenience's sake. Dragon Pulse hits Kingdra for maximum damage, Surf is a back-up water move and Hypnosis is to add some status on the side. A Timid nature allows Milotic to outspeed the neutral natured base 90 speed group, as well as slower members of the base 100 speed group. While this job may be better off left to another team member, Milotic can still pull it off due to inherent defensive capabilities.
Extra Options
Light Screen is always an option to support your team, replace it with your status move if you plan on using it. Hydro Pump gives a little boost in power, but for a dedicated tank it makes little sense to use the move. Milotic can Haze, but the effectiveness of the move in the standard metagame is questionable. Hidden Power Grass can be used for Swampert, but it is not a recommended choice.
EVs
For defensive sets, increasing the substandard physical defense is a must. The rest varies on what exactly you want Milotic to do. The HP numbers given for every set provide optimum recovery and the rest has been generally dumped in the other defense. You may remove the Sp. D EVs to be placed into attack if you think you need the power.
Troublesome Pokemon
Milotic's main issue is other special tanks who stop it in it's tracks. Thankfully, these rarely have the ability to do anything to you. Physical attackers and special attacks alike can't get a safe switch in on Milotic due to the unpredictable nature of it's attacks and statuses. Out of the special walls in today's game, Snorlax is the most threatening, as it can increase stats while you're forced to switch out. Raikou is also a bother, though a well timed Toxic should put him out of service. Beware Heracross and his Guts ability and high special defense, a wrong move could lead to your team getting swept.