Miltank
Thick Fat
Halves Ice and Fire damage.
Type Tier
Normal BL
Statistics
Min- Min Max Max+
HP
95
 - 331 394 -
Atk
80
 176 196 259 284
Def
105
 221 246 309 339
SpA
40
 104 116 179 196
SpD
70
 158 176 239 262
Spe
100
 212 236 299 328
Name Item Nature

Curser

 Leftovers Impish
Moveset EVs
~ Curse
~ Body Slam
~ Milk Drink
~ Heal Bell
220 HP / 192 Atk / 96 Def

Cursing Miltank is probably the best option. It can hold its own against things like Salamence and Blissey with Milk Drink and Curse. Watch out for Skarmory, but that is a given.

Name Item Nature

Psych Upper

 Leftovers Impish
Moveset EVs
~ Psych Up
~ Body Slam
~ Earthquake
~ Milk Drink
220 HP / 192 Atk / 96 Def

You can steal Tyranitar / Salamence Dragon Dances, Snorlax / Swampert Curses, Suicune Calm Minds, and many other things. Miltank is fast enough to take advantage of Tyranitar Dragon Dances as well.

Other Options

It can Thunder Wave, if you are into that. Shadow Ball can take care of Ghosts.

EVs

Lots of Defense, HP, and Attack.

Opinion

Miltank is good if used correctly, which means you aren't using Thunder Wave / Seismic Toss. Seriously, Blissey does that 104129480712x better than Miltank. If you want to use Miltank, use its natural advantages over Blissey or don't use it at all.

Counters

Skarmory, Choice Band Metagross, Gengar, and Celebi; for the majority of stupid Miltank that use Seismic Toss / Thunder Wave: Snorlax, Swampert, Suicune, Milotic, Vaporeon, Celebi.