dreadful vs frightful

dreadful

• Unpleasant, awful, very bad (also used as an intensifier). 

• Genuinely horrific, awful, or alarming; dangerous, risky. 

• Dreadfully. 

• A shocking or sensational crime. 

• A journal or broadsheet printing such reports. 

• A shocker: a report of a crime written in a provokingly lurid style. 

frightful

• Unpleasant, dreadful, awful (also used as an intensifier). 

• Genuinely horrific, awful, or alarming. 

• Frightfully; very.