These are illegal acts or heinous offences which attract or carry severe punishments or penalties. Crimes like murder, armed robbery and kidnapping could attract death penalties.
Other kinds of criminal offences that could attract jail sentences, payment of time or both are sedition, libel, slander, 419 (advanced fee fraud), embezzlement of public funds, money laundering, importation of firearms or its possession, rape, examination malpractices, drug peddling, child/female trafficking, cultism, impersonation, arson, treason, forgery, smuggling of contraband goods etc.