Denshi Jisho — Online Japanese dictionary

がい injury; harm; evil influence; damage
Common word, Noun 
がいい malice; malicious intent; intent to kill
Noun 
がいす 1: to injure; to damage; to harm; to hurt;
2: to kill;
3: to hinder; to obstruct
Godan verb with su ending, Transitive verb 
がいあく harm; injury; evil (influence)
Noun 
がいぎょ harmful fish (e.g. non-native and prolific, etc.)
Noun 
がいしゃ victim of a crime
Noun 
がいしん evil intentions; malice
Noun 
がいどく harm; injury; mischief; poison; virus
Noun 
する がいする 1: to injure; to damage; to harm; to hurt;
2: to kill;
3: to hinder; to obstruct
Common word, Suru verb - special class, Transitive verb 
がいちゅう harmful insect; noxious insect
Common word, Noun, No-adjective 
がいじゅう harmful animal
Noun 
がいちょう vermin; injurious bird
Noun 
を及ぼす がいをおよぼす to cause harm (to)
Expression, Godan verb with su ending 

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