That -X can devastate most opponents by wiping out their colored cards, which is likely to be most of them
Even if Kaito's triggered ability triggers more than once in the same turn (perhaps because one or more attackers had first strike, multiple players were dealt combat damage by your creatures, or there were multiple combats), and you return an attacking creature to hand each time, you won't be able to activate Kaito's loyalty abilities more than twice that turn
Although the board presence gained from using her -3 ability is strong, sometimes it wont hit a relevant creature and leave itself open for attack
Fatal Grudge sort of falls into that group
A 6/6 flier can put in some good work itself, but this one occasionally misses the mark and comes down as a 3/3 instead
While youre usually trading card efficiency for mana efficiency with pitch cards like this one, other free spells that well cover later make this feel markedly less appealing