Radiant Strike

The "tapped creature" clause is the whole design conversation here. Unconditional creature removal at instant speed for four mana has always been priced above what this rate offers, so the restriction is the cost of the flexibility: this can only kill something that has already committed by attacking or by tapping for an ability, not something sitting untapped on defense. That makes it a combat-and-tempo answer rather than a proactive one. Point it at an attacker after it swings, and the three life stapled on turns the removal into a defensive lifeline; but it will never stop a fresh threat the turn it resolves, and an untapped blocker escapes it entirely, since blocking does not tap the creature. The artifact half is the more open clause, killable regardless of tap status, and it gives the card a floor as noncreature disruption when the creature mode is dead. The lifegain is the padding that lets it sit in slower white decks, where a tempo-neutral four-mana instant is already asking you to play from behind. It belongs to a long white tradition of removal that only answers what has already tapped, trading raw efficiency for a stapled rider and a wider net of legal targets. This version leans on that breadth rather than speed, folding the two things white most reliably wants gone (a threatening attacker and a problem artifact) into a single card.