Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Scythe Specter

Flying
Whenever Scythe Specter deals combat damage to a player, each opponent discards a card. Each player who discarded a card with the highest mana value among cards discarded this way loses life equal to that mana value.

Killing Wave

For each creature, its controller sacrifices it unless they pay X life.

Browbeat

Any player may have Browbeat deal 5 damage to them. If no one does, target player draws three cards.

Choice of Damnations

Target opponent chooses a number. You may have that player lose that much life. If you don't, that player sacrifices all but that many permanents of their choice.

Sin Prodder

Menace
At the beginning of your upkeep, reveal the top card of your library. Any opponent may have you put that card into your graveyard. If a player does, Sin Prodder deals damage to that player equal to that card's mana value. Otherwise, put that card into your hand.

Rakdos, Patron of Chaos

Flying, trample
At the beginning of your end step, target opponent may sacrifice two nonland, nontoken permanents of their choice. If they don't, you draw two cards.

Do or Die

Separate all creatures target player controls into two piles. Destroy all creatures in the pile of that player's choice. They can't be regenerated.

Temporal Extortion

When you cast this spell, any player may pay half their life, rounded up. If a player does, counter Temporal Extortion.
Take an extra turn after this one.

Combustible Gearhulk

First strike
When Combustible Gearhulk enters, target opponent may have you draw three cards. If the player doesn't, you mill three cards, then Combustible Gearhulk deals damage to that player equal to the total mana value of those cards.