Both excoriating and coruscating are verb forms used as adjectives.
Excoriating is a hideous word. At least, its meaning is:
excoriate (transitive verb): to pull off the skin or hide from (a man or beast)
The word retains this literal meaning in the context of pathology to refer to the removal of skin by cutting, abrasion, or corrosion:
Gastric secretions leaking around the gastrostomy can result in skin excoriation.
Excoriate can also mean to strip bark from a branch or other part of a plant:
A tree which does not fructify is often rendered fertile by an excoriation near its root.
In general usage, excoriate is frequently used figuratively to mean, “to upbraid scathingly, decry, revile”:
Feinstein excoriates CIA for spying on Senate committee
Kerry excoriates Assad regime for ‘inexcusable’ chemical strike
Coruscating, on the other hand, is a pretty word:
coruscate (intransitive verb): to give forth intermittent or vibratory flashes of light; to shine with a quivering light; to sparkle, glitter, flash.
From the Latin verb coruscare, “to vibrate, glitter, sparkle, gleam,” coruscate and its forms (often misspelled with two r’s) are used to describe lighting effects:
now, when the ground was white with snow, and the forest trees covered with ice, and sparkling and corruscating [sic] in the rays of the sun, Nettie would shout with delight…
below, by the creek, a corruscating [sic] tendril of smoke drifted up through the trees.
Figuratively, coruscating describes a lively witty writing style, the kind demonstrated by Oscar Wilde in The Importance of Being Earnest, a play devoid of malice.
Ambrose Bierce and H.L. Mencken, on the other hand, made use of a lively, quick-witted coruscating style to excoriate the people and institutions they despised. For this reason the pretty word coruscating and the ugly word excoriating have collided like chocolate and peanut butter in a Reese’s candy ad.
A few journalists seem to understand the meaning of coruscating, but a great many use it as if it meant excoriating:
Michael Moore’s coruscating attack on the gun culture, Bowling for Columbine.
[Julia Gillard] launched a coruscating attack in parliament on opposition leader Tony Abbott
Iain Macwhirter launches coruscating attack on Alex Salmond and Rupert Murdoch
Betsy Andreu, the wife of Lance Armstrong’s former team-mate Frankie, who played a key part in exposing the Texan as a drug cheat, has launched a coruscating attack on the disgraced cyclist.
Because of the confused idea that coruscating has something to do with negative comments, the word is frequently paired with review, critique and criticism:
The Australian literary critic Clive James… manages to produce coruscating reviews like his brutal attack on Dan “Da Vinci” Brown’s novel Inferno.
But the most coruscating criticism came from Ankie Spitzer and Ilana Romana, two of the widows of the Munich Eleven
Wow, a coruscating criticism of Sony’s PS4
Another possible reason for the frequent misuse and misspelling of coruscate could be that speakers associate it with the meaning and spelling of corrosion.
In the interest of saving coruscating to mean sparkling, the next time you want to characterize a verbal attack as extremely scathing, use excoriating. When you do have occasion to use coruscating, remember to spell it with one r.