horrendous

As adjectives the difference between tragic and horrendous

is that tragic is causing great sadness or suffering while horrendous is extremely bad; awful; terrible.

As a noun tragic

is (obsolete) a writer of tragedy.

As adjectives the difference between horrendous and horrifying

is that horrendous is extremely bad; awful; terrible while horrifying is tending to inspire horror; that horrifies; horrific.

As a verb horrifying is

present participle of lang=en.