for example i may have a slaking with return hammer arm e quake and shadow claw (im not sure it can learn them moves its just a example)
return=normal-supper effective on nothing 0 e quake=ground-supper effective on-poison fire steel rock electric 5 shadow claw=ghost-supper effective on-ghost psychic 2 hammer arm=fight-supper effective on-rock steel dark 3 -2 because ground covers rock and steel so overall the slaking covers 8 types is there a pokemon which has a movest which covers 14/18 and above types considering they are just 1 type for example tangroth grass (allowed) bulbasaur grass poison not aloud
Rock Fighting Ice and Ground. 0 No effect (Shedinja) 0 Not Very Effective 158 Normal Effectiveness 505 Super Effective http://pokemondb.net/tools/type-coverage
I found another set.
water,electric,fighting and flying
No Effect 0
Not Very Effective 0
Normal Effectiveness 160
Super Effective 505
You can use the pokemon mew for instance. Smeargle also works.
Ghost, Ice, Fighting, Ground
0 No effect
0 Not Very Effective
153 Normal Effectiveness
512 Super Effective