The finishing blow is to cast a huge Murktide Regent for cheap and have counterspells to protect it for the win
Duplicant, Meteor Golem, Kozilek, the Great Distortion, Ugin, the Ineffable, Spatial Contortion, Warping Wail, Titan's Presence, Desecrate Reality, Rise of the Eldrazi, Unstable Obelisk, Steel Hellkite 11 targeted removal
While its going to be incredibly difficult to edge out Kumena as the most popular Merfolk Commander (especially with Deeproot Pilgrimage in the main set offering a serious upgrade), Hakbal makes a strong case
If this card isn't cEDH playable, you can feed me to a book-loving spirit beast
Hydro-Man, Fluid Felon Blue has very few mana dorks, but Hydro-Man, Fluid Felon is one of the strongest
Sword of the Animist is also popular in equipment decks and beyond, anywhere that needs more ways to build their mana pool