Grievous

[Britney]

Causing grief or sorrow; painful; afflictive; hard to
bear; offensive; harmful.

[Lanell]

having very serious effects or causing great pain:

[Agnes]

(of something bad) very severe or serious.

[argey]

of great gravity or crucial import; requiring serious thought

[Couch Potatoe]

shockingly brutal or cruel

[MonicaLes]

Serious, grave, dire or dangerous.

[juan98]

General Grievous is a character and antagonist in the Star Wars franchise created by George Lucas. Grievous was introduced in the 2003 animated series Star Wars: Clone Wars (voiced by John DiMaggio in the second season and Richard McGonagle in the third season), before appearing through computer-generated imagery in the 2005 live-action film Star Wars: Episode III – Revenge of the Sith (voiced by Matthew Wood). Wood reprised his role in the 2008 computer animated series Star Wars: The Clone Wars.
General Grievous is depicted as a brilliant military strategist who serves as the Supreme Commander of the Confederacy of Independent Systems Droid Armies during the Clone Wars. He is a powerful Kaleesh cyborg who has mastered all forms of lightsaber combat under the tutelage of Count Dooku to rival the Force abilities of the Jedi of the Galactic Republic. Grievous harbors an intense hatred of the Jedi and gains a reputation as a feared and ruthless Jedi hunter who collects the lightsabers of his fallen victims as trophies. He develops a rivalry with Jedi Master Obi-Wan Kenobi, whom he clashes with numerous times during the war, and is killed by Kenobi during their final confrontation in Revenge of the Sith.
The character has become one of the franchises most iconic villains and his popularity within the Star Wars fandom has earned him a cult following. In addition to the film and the animated series, General Grievous has appeared in various forms of media in the Star Wars Expanded Universe, including novels, comic books and video games. Such works explore his past as a reptilian warlord named Qymaen jai Sheelal who grew to despise the Jedi for causing the plight of his people. A ship crash secretly orchestrated by Count Dooku mortally wounds Grievous and leads to his reconstruction as a cyborg. This origin story was retroactively altered in The Clone Wars, in which it is implied that Grievous willingly augmented his body with cybernetic enhancements to rival the Jedi. Several elements of his original backstory were later reintegrated into the current Star Wars canon.

[KalanNug]

characterized by great atrocity; heinous; aggravated; flagitious; as, a grievous sin

[Franceswah]

full of, or expressing, grief; showing great sorrow or affliction; as, a grievous cry

[GrokLuth 0]

Grievous refers to something that is causing severe pain, suffering, or sorrow. It can also mean something serious, dire or grave, characterized by severe seriousness or solemnity. In some contexts, it may also refer to something outrageously bad or reprehensible.