According to the article by Andriy Slynchuk, the five most serious online crimes are:

1. Illegally using streaming services and torrent sites to access copyrighted content because it deprives the content creators of their rightful compensation which can lead to legal consequences for users.

2. Cyberbullying and trolling can cause emotional distress and lead to criminal charges.

3. Identity fraud and impersonation where you use someone else’s information without their knowledge for deceptive purposes. This can lead to consequences for the victim and the perpetrator.

4. Collective information about children under 13 without parental consent violates the Children’s online protection act.

5. Conducting illegal internet searches may also be monitored by authorities and can lead to a criminal investigation.