お人好し（おひとよし）

“お人好し” means a person does things out of kindness, which is good. But sometimes, the people they help just want to take advantage or get rid of their own problems. So, even though being kind is not bad, it can end up helping people who only think about themselves. This conveys the nuance that "お人好し" can sometimes support the wrong kind of behavior in others.

彼はお人好しだから同僚から仕事を押し付けられている。
かれはおひとよしだからどうりょうからしごとをおしつけられている。
He is so gullible that his colleagues always push work onto him.