First time commenter here...

My son got me into MTG and into EDH and he was making decks that I found very overwhelming to play against. He's 14 and has built a very good (imho) Kruphix deck and zombie (Lilliana?) deck.

My favorite combos are from the Mirko EDH deck I built that was finally able to beat him consistently enough that he no longer wanted to play against it. In its current form it can mill you in a number of ways, some using combos...

[[Duskmantle Guildmage]] + [[Mindcrank]] = Infinite Mill Combo

[[Traumatize]] + [[Keening Stone]] = 2 step mill win

[[Tunnel Visions]] + [[Precognition]] or any of a number of cards where you put an opponent's card on the bottom of their graveyard = instant mill win

The deck is chock full of other mill options, and obviously there are ways to try to avoid getting milled, but I really really enjoyed researching this particular playstyle and assembling a deck that was so effective my son kind of hates playing against it.

It was fun, but I complied and have built other decks so our games are fun. The process, and just learning more about the game in general, has taught me that certain playstyles (mill, control) are uniquely frustrating to play against.

I don't feel bad for subjecting him to my mill deck but now I better understand why he hated it so much. It's like your hope is slowly draining away and there's little you can do to stop it...

Side note - our games were generally 1 v 1 and it's clear to me that a mill deck in multplayer commander (the more traditional way to play EDH) would probably not be terribly effective. Against a single opponent though it actually worked remarkably well!