The very best commander for the sliver tribe is the Cascade card, The First Sliver
Basically, in a perfect world, we'll get Sanctum of Fruitful Harvest and Sanctum of Calm Waters going first, and maybe even Sanctum of All, and then Sanctum of Shattered Heights and Sanctum of Stone Fangs will come down to close out the game
Spider-Punk Spider-Punk exists for anyone who really wants to stop counterspells, or for anyone whos ever wanted to go to a spider rave with a bunch of rioting arachnids
Once a player has a speed trait, they can increase it once on each of their own turns by causing an opponent to lose life
Control decks can also be a problem, as one of the best ways to disrupt control, forcing them to play cards on their turn, is hard for Reanimator decks to do, meaning that sometimes it becomes a waiting game of baiting your control playing opponent into taking action before you do, but even that might be difficult as many control decks forms of removal do so by Exile, not destroying things
If your deck isn't consistently relevant by turn 3, it's not competitive