Unreasonable behaviour refers to the behaviour by one spouse that makes it unreasonable to expect the other spouse to continue living together.

Each case depends on its own facts. It would be best to seek independent legal advice if you require advice on the merits of your case.

You may wish to read more about this at https://www.judiciary.gov.sg/family/understand-requirements-getting-divorce and https://www.judiciary.gov.sg/judgments/FJC-case-highlights/CaseHighlightSubjectAreas/divorce---facts.