Grabbing a creature like Gishath, Sun's Avatar from your deck and putting it into play to quickly overwhelm the board
1st Edition symbol borrowed from shiningbill
Meanwhile, Izzet Charm can still counter that planeswalker (admittedly in a much less efficient way since it costs twice as much as Spell Pierce does), but it can also kill the Dark Confidant and, when the other modes are dead, potentially improve your hand by looting away some extra lands, Faithless Lootingstyle
Lulu, Stern Guardian* From the Final Fantasy 10 Commander Deck, Lulu here is an interesting combat deterrence card, and has a powerful proliferation activated ability that is of great use to counter decks, and poison decks
Mono-colored decks might struggle to reach seven unique lands, but thats no problem for anything with two or more colors