Terrible = extremely bad or serious, causing great fear or horror.

• The heat is terrible in Delhi during summer.
• What terrible food they gave us!
• His behaviour is terribly bad.
• The weather in Nagaland is terrible during winter.

Terrific = very good, great, causing fear.

• Mammootty looked absolutely terrific in the movie ” Oru vadakkan veeragadha”.
• This book is going to have a terrific influence on the youth.
• They chased the robbers at terrific speed.
• You have got a terrific opportunity to fly to the US.
• Dr.K.J.Yesudas , popularly known as ‘Ganagandharvan’ , is a terrific Indian playback singer and an accomplished Carnatic musician.