54 cards where the color identity is BR and it’s legal in Brawl and the card types include “legendary” and (the card types include “creature” or the card types include “planeswalker”)

Juri, Master of the Revue (Commander Legends #282)
Kalain, Reclusive Painter (Adventures in the Forgotten Realms #225)
Kroxa, Titan of Death's Hunger (Theros Beyond Death #221)
Mauhúr, Uruk-hai Captain (The Lord of the Rings: Tales of Middle-earth #214)
Valki, God of Lies // Tibalt, Cosmic Impostor (Kaldheim #114)
Valki, God of Lies // Tibalt, Cosmic Impostor (Kaldheim #114)
Vial Smasher, Gleeful Grenadier (Outlaws of Thunder Junction #235)
Zoyowa Lava-Tongue (The Lost Caverns of Ixalan #245)
Ayara, Widow of the Realm // Ayara, Furnace Queen (March of the Machine #90)
Ayara, Widow of the Realm // Ayara, Furnace Queen (March of the Machine #90)
Crucias, Titan of the Waves (Alchemy: The Brothers' War #18)
Florian, Voldaren Scion (Innistrad: Midnight Hunt #223)
Judith, the Scourge Diva (Commander Masters #341)
Lagomos, Hand of Hatred (Dominaria United #205)
Laughing Jasper Flint (Outlaws of Thunder Junction #215)
Neheb, the Worthy (Amonkhet #203)
Ob Nixilis, the Adversary (Streets of New Capenna #206)
Olivia, Mobilized for War (Shadows over Innistrad #248)
Rivaz of the Claw (Dominaria United #215)
Rowan, Scion of War (Wilds of Eldraine #211)
Totentanz, Swarm Piper (Wilds of Eldraine #216)
Akul the Unrepentant (Outlaws of Thunder Junction #189)
Angrath, Captain of Chaos (War of the Spark #227)
Anje, Maid of Dishonor (Innistrad: Crimson Vow #231)
Chainer, Nightmare Adept (Modern Horizons 2 #289)
Garna, Bloodfist of Keld (Dominaria United #200)
Hidetsugu, Devouring Chaos (Kamigawa: Neon Dynasty #99)
Kardur, Doomscourge (Kaldheim #216)
Kethek, Crucible Goliath (Phyrexia: All Will Be One #206)
Mishra, Claimed by Gix (The Brothers' War #216)
Ob Nixilis, Captive Kingpin (March of the Machine: The Aftermath #41)
Orcus, Prince of Undeath (Adventures in the Forgotten Realms #229)
Prosper, Tome-Bound (Forgotten Realms Commander #2)
Shagrat, Loot Bearer (The Lord of the Rings: Tales of Middle-earth #228)
Uglúk of the White Hand (The Lord of the Rings: Tales of Middle-earth #235)
Angrath, the Flame-Chained (Rivals of Ixalan #152)
Garna, the Bloodflame (Dominaria United Commander #151)
Judith, Carnage Connoisseur (Murders at Karlov Manor #210)
Mishra, Tamer of Mak Fawa (The Brothers' War #217)
Obosh, the Preypiercer (Ikoria: Lair of Behemoths #228)
Rakdos, the Muscle (Outlaws of Thunder Junction #226)
Rankle and Torbran (March of the Machine #252)
Raphael, Fiendish Savior (Commander Legends: Battle for Baldur's Gate #292)
Sauron, the Lidless Eye (The Lord of the Rings: Tales of Middle-earth #288)
Sethron, Hurloon General (Jumpstart #25)
The Balrog, Flame of Udûn (The Lord of the Rings: Tales of Middle-earth #297)
The Scorpion God (Hour of Devastation #146)
Angrath, Minotaur Pirate (Rivals of Ixalan #201)
Olivia, Crimson Bride (Innistrad: Crimson Vow #245)
Rakdos, Patron of Chaos (Murders at Karlov Manor #224)
Rakdos, the Showstopper (Ravnica: Clue Edition #205)
Zagras, Thief of Heartbeats (Zendikar Rising #241)
Bladewing the Risen (Iconic Masters #193)
Kazarov, Sengir Pureblood (Dominaria #96)
Mishra, Lost to Phyrexia (The Brothers' War #163b)
The Balrog, Durin's Bane (The Lord of the Rings: Tales of Middle-earth #195)

This search is finished. Now the real work can begin.