mtg meta commander decks Magic: the Gathering Fill your graveyard and avenge the dead with Graveyard Overdrive Most Hated Magic the Gathering

They may do something else with their turn besides kill Nissa, thinking they have another turn until shes actually a threat, but Ulvenwald Hydra typically throws a wrench into their plans

That could easily be a 5/5 or 6/6 bonus to your Commander plus the boosts and equipment from other places for a Commander kill in one hit, or two with two attacks

Copying artifacts and enchantments can get out of hand, though this is all fiddly enough that I wouldnt expect it to be too problematic

Less exciting but still solid is Impossible Inferno

Graded Population Report: Wakka, Devoted Guardian [Foil] #97 Visualize the distrbution of grades in the chart

The most obviously powerful one of these is Syvelun of Sea and Sky, which is basically an indestructible merfolk that draws cards and helps protect your other creatures