Magic: the Gathering has many cards which do similar things. Bitter Feud is one such card that acts as a sort of redundancy for existing cards. To be fair, Bitter Feud is one exclusive card from the Commander 2014: Built from Scratch deck that took time to find some love. Its effect is essentially the same as Furnace of Rath and Dictate of the Twin Gods, which double damage done to players and permanents.
The difference with Bitter Feud is that it designates two players rather than affecting all players. In a multiplayer environment, it would only affect the players you choose. That means only one opponent will benefit from the effects of the doubled damage.
You could argue that Furnace of Rath and Dictate of the Twin Gods are enough in one deck for this sort of effect. In EDH, however, having redundancy is important when you only have one copy of each card that isn’t a basic land. In a one-on-one setting, it’s understandable how Bitter Feud would be too redundant. If you have all three of these cards on the board, you’re increasing damage by eight whole times.
Bitter Feud is definitely a fun Commander card in that it essentially puts two players into a life-and-death struggle. In 1v1 Commander, this is a particularly interesting card to consider, as long as the deck playing it can deal damage very quickly. It’s a well-designed card for multiplayer Commander politics, and can be a deadly weapon in 1v1 Commander when deployed correctly.
As far as decks that actually have played Bitter Feud with any regularity, Heartless Hidetsugu was the first Commander to top the list. Since his ability deals damage equal to half of each player’s life total (rounded down), his deck absolutely loves any additional damage-doubling effect it can get. Other decks including this card include Fumiko the Lowblood, Xantcha, Sleeper Agent, and Kazuul, Tyrant of the Cliffs.
While aggressive burn lists aren’t extremely popular in the Commander format, they do exist. If ending games quickly by doubling damage is something you want to do, then Bitter Feud is definitely worth a look to play alongside other damage-doublers such as Furnace of Rath and Dictate of the Twin Gods.