Switch into anything (maybe not megahorn) and tank it and if not focus sash will leave with one health, Set up aqua ring, or recover depending on damage taken and just spam aqua tail
Impish you mean. Also, why would you use an Impish Milotic? ._. Milotic is best at special attacking; its physical Attack isn't that good. Also, it's bulky enough that it doesn't need Focus Sash. Hydro Pump/Surf/Scald >>>>>>>>>>>> Aqua Tail.
EVs: 40 HP/224 Atk/16 Def/228 Spe
Ability: Swift Swim
Kingdra 4x resists Milotic's STAB and can easily use it as setup fodder for Sub + DD (given the lack of Dragon Pulse or Ice Beam, this shouldn't be hard), then proceed to wreck it with STAB Outrage.