astounding (adj.)

• amazing
• appalling
• astonishing
• awe-inspiring
• awesome
• awful
• breathtaking
• confounding
• dire
• direful
• dread
• dreaded
• fell
• formidable
• ghastly
• ghoulish
• grim
• grisly
• gruesome
• hideous
• horrendous
• horrible
• horrid
• horrific
• horrifying
• macabre
• mind-boggling
• miraculous
• morbid
• overwhelming
• prodigious
• redoubtable
• shocking
• spectacular
• staggering
• startling
• stunning
• stupendous
• surprising
• terrible
• terrific
• tremendous
• wonderful
• wondrous