Jund has long been one of the most successful decks in Modern, but the format continues to shift away from that strategy. The mana base requires 3 colors, and Tarmogoyf has been losing appeal in the face of Fatal Push and Path to Exile. Dropping the green and playing straight B/R with all creatures that create value on their own may be the next iteration.
Dark Confidant is the central carryover from Jund to straight B/R. Confidant is a must-answer threat that can take over the game. When you’ve got tons of 1-for-1 removal and creatures that can push your advantage, all you need to do is draw extra cards.
A turn-2 Pack Rat could be enough to end the game with just a single additional land drop. We saw the strength of curving a 1-mana discard spell into Pack Rat during the Mono-Black Devotion days of Standard. Decks aren’t built deal with multiple Pack Rats, so it can completely take over in fair matchups. With plenty of 1-mana interactive spells, you can easily flood the board with Rats while still casting spells.
Discard and removal clear the way for Goblin Rabblemaster to take over. Untapping with the Rabblemaster on an empty board will create tons of damage on turn 4 and the ability to close out the game on turn 5.
Olivia Voldaren and Chandra, Torch of Defiance sit at the very top of your curve. You don’t want too many 4-drops with a playset of Dark Confidants, but both of these are good options against any creature deck. Olivia is yet another creature that demands an answer in any creature matchup or the game will spiral out of control for the opponent. Chandra can tick up or down for value, killing creatures or drawing cards, and dealing damage to the opponent until they’re done.
Fatal Push is your best removal spell, as it’s a perfect way to deal with big creatures like Tarmogoyf and Death’s Shadow for a minimal investment. Terminate costs an extra mana, but makes sure you don't miss anything. This is important as Gurmag Angler and Tasigur become more heavily played. Dreadbore gives you a sorcery-speed Terminate that can deal with all of the Gideons and Lilianas floating around.
Just 2 copies of Lightning Bolt would have been considered blasphemous a few years ago, but it makes complete sense now. It kills fewer and fewer of the most commonly played creatures, but a 1-mana spell and reach are still great with Rabbles and Confidants.
Liliana of the Veil is a busted 3-mana planeswalker. It can finish off an opponent’s hand or kill whatever threat they have on the board (pairing well with the other cheap removal spells), making it a formidable threat for a low cost in just about every matchup.
Going down to two colors allows you to play more basics and gives you the option of playing a powerful disruption spell in Blood Moon. The Moon can completely win the game against decks like Tron or Valakut, but it also wrecks creaturelands and a variety of intense mana bases in the format. Curving discard spell into any of the 2-drops into Blood Moon is as good a start as you can ever get in the format!
Pairing the black discard spells and removal with any color is going to give you a solid deck in Modern, but going straight red to focus on Blood Moon is an excellent approach to the format.