Boltwave

In Commander, Boltwave is purpose-built: hitting three opponents at once multiplies its damage output by a factor that no 60-card format can match, and the spell-count payoff aligns cleanly with the spellslinger and storm archetypes that thrive at the multiplayer table. In Modern and Pioneer, Boltwave competes with faster, unconditional burn that doesn't require setup — it can close a game when you're already casting four spells in a turn, but that condition is harder to manufacture consistently in a two-player context. Legacy and Vintage have the raw spell density to make it genuinely threatening, though both formats offer more efficient finishers, so Boltwave is a fringe consideration at best. Standard is the format where it has the most room to establish itself, since the card pool is shallow enough that a scalable damage spell with no ceiling sees real play.