Which dual types have the most & least weaknesses?

Question

Like for example the best is Dark+Ghost - No weaknesses

Which dual type has the most weaknesses?
Which dual type not including dark ghost has most resistances?
Which dual type covers most Pokemon with its standard type moves?
Which dual type covers the least?

For you who don't know dual type is a Pokemon with two types

Answer 1

Most Weaknesses: Grass-Psychic(Celebi, Exeggcute, Exeggutor) and Grass-Ice(Snover, Abomasnow) 7 Types super effective(Note both have a 4x weakness)

Most resistances: Steel-electric(Magnezone family) 13 Resistances and an immunity

Most Neutral coverage: Ice-Electric(Rotom-F), Fire-Dragon(Reshiram), Water-Normal(Bibarel), Fighting-Fire(Infernape, Monferno, Blazekin, Combusken, Emboar, Pignite), Dragon-Ground(Garchomp family, Flygon), Normal-flying(Lots)

Least Neutral coverage: Dark-Ghost(Spiritomb, Sableye), Poison-Steel(None)

I hope this helps :)

Note(If I missed anything please comment)

Comments

Not really something you missed but magnet one can have 2 immunity with magnet rise thanks:)

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Rotom-F is Ice/Electric

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Water/Ground has 4X weakness to grass

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Vibrava is Dragon/Ground, too.

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So? That's the Flygon family, and he mentioned Flygon........

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I would just like to ask where Magnezone's 12th and 13th resistances are? It has 11 resistances and 1 Immunity. It can get another immunity from magnet rise. That would make 11 resistances and 2 immunities which would make 13 resistances in total. Is this what you meant by the 13 and 1 immunity if so you may need to reword the Magnezone bit.

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@leopgiles look at the timestamp on the answer. This was posted before the release of Gen.6, where steel still resisted dark and ghost, both adding to magnezone's list of resistances.