noun
chronic complainer; person who makes unreasonable complaints
Wasei-eigo from English 'claimer'. Refers to someone who habitually complains, often unreasonably, especially to businesses or service providers. Carries a negative connotation.
wasei-eigo (Japanese-coined English), from claimer
あの客はクレーマーだから、対応に気をつけて。
That customer is a chronic complainer, so be careful when dealing with them.
クレーマーからの電話が
We get calls from unreasonable complainers almost every day.