Death Kiss 

Creature — Beholder
Whenever a creature an opponent controls attacks one of your opponents, double its power until end of turn.
{X}{X}{R}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, goad up to X target creatures your opponents control.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Overclocked Electromancer 84%
$0.33#10716
"Whenever this creature attacks, double its power until end of turn."
Seifer Almasy 83%
$0.23#10671
"Whenever a creature you control attacks alone, it gains double strike until end of turn."
Rafiq of the Many 83%
$0.29#10463
"Whenever a creature you control attacks alone, it gains double strike until end of turn."
Squall, SeeD Mercenary 83%
$0.78#3820
"Whenever a creature you control attacks alone, it gains double strike until end of turn."
Aradesh, the Founder 83%
$0.26#13302
"Whenever a creature you control attacks, if it enlisted a creature this combat, the creature that attacked gains double strike until end of turn. If that creature's power is 4 or greater, draw a card."
War-Trained Slasher 82%
$0.13#24247
"Whenever this creature attacks a battle, double its power until end of turn."