Sen Triplet Stax (EDH / Commander)

This deck is designed to stop the combo deck from winning, by slowing down the game, and then eliminating all of their win conditions. You're going to want to start off by playing some low-cost stax effects (Cursed Totem, Trinisphere, Spirit of the Labyrinth), to give everyone more time to actually play the game. Once that's set up, keep the stax coming, but also set up some card draw effects (Consecrated Sphinx, Rhystic Study). You're going to be fishing for the winning combos.

Thopter Assembly + Time Sieve = Infinite Turns

Pili-Pala + Grand Architect = Infinite colored mana

Basalt Monolith + Rings of Brighthearth = Infinite colorless mana

With infinite mana, you can win with either Exsanguinate or Walking Ballista.

Now, for some of the fun stuff you can do with your commander. Playing Telepathy will reveal everyone's hands. This means you'll be able to see who the threat is, but also, who has the best stuff. When Sen Triplets comes out, you can play your opponent's lands, creatures, and win conditions. Play Mycosynth Lattice, Chromatic Lantern, or Celestial Dawn so that colored mana won't be a restriction. You could cast your opponent's decimate if you wanted to.