The heroine may call the hero a blackguard at first, but in the end only the villain fits the description.

Merriam-Webster

A rude or unscrupulous person : a person who uses foul or abusive language

Wiktionary

A vulgar and uncouth person. One who has a less than trustworthy level of inhibition.

1811 Vulgar Tongue

Black guard — A shabby, mean fellow; a term said to be derived from a number of dirty, tattered roguish boys, who attended at the Horse Guards, and Parade in St. James’s Park, to black the boots and shoes of the soldiers, or to do any other dirty offices. These, from their constant attendance about the time of guard mounting, were nick-named the black-guards.

Another fun, foppy term, but with more history.

1811 Vulgar Tongue

Maccaroni (sic). An Italian paste made of flour and eggs. Also a fop: which name arose from a club, called the Maccaroni Club, instituted by some of the most dressy travelled gentlemen about town, who led the fashions; whence a man foppishly dressed, was supposed a member of that club, and by contraction styled a Maccaroni.

Merriam-Webster

A member of a class of traveled young Englishmen of the late 18th and early 19th centuries who affected foreign ways b : an affected young man : FOP

Wikipedia

In 18th century England, a macaroni was a fashionable man who dressed and even spoke in an outlandishly affected manner. The term pejoratively referred to a person who exceeded the ordinary bounds of fashion in terms of clothes, eating and gambling. Young men who had been to Italy on the Grand Tour adopted the Italian word and said that anything that was fashionable or à la mode was ‘very macaroni’. The expression was particularly used to characterize those people who dressed in high fashion with stripes and tall, powdered wigs with a little hat on top which was so high that it could only be removed on the point of a sword. Macaronies combined the enjoyment of wine, sex and song with effeminacy of dress. They are a precursor to the dandy.
The song Yankee Doodle from the time of the American Revolutionary War talks of a man who stuck a feather in his hat and called it Macaroni. This shows that “Macaroni” at the time was a slang term for the most up-to-date of fashions.

As if the word fop isn’t fun enough…

1811 Vulgar Tongue

Anciently, a fool. Fools, in great families, wore a cap with bells, on the top of which was a piece of red cloth, in the shape of a cock’s comb. At present, coxcomb signifies a fop, or vain self-conceited fellow.

Merriam-Webster

A conceited foolish person : fop

The man that wants to be a dandy, but goes a little too far. If the hero is a fop in the first pages, he is most likely in disguise.

Merriam-Webster

A foolish or silly person : a man who is devoted to or vain about his appearance or dress : coxcomb, dandy

Wikipedia

The fop is a stock character who appears from time to time in fiction. He is a person who makes a habit of fastidiously overdressing and putting on airs, aspiring to be viewed as an aristocrat. In English, the word fop is older, but the meaning of an overdressed, frivolously fastidious man may not be; Shakespeare’s King Lear contains the word, in the general sense of a fool. Osric in Hamlet has a great deal of the manner.

Note: Fop is not defined in the 1811 Vulgar Tongue, even though it is referenced throughout under Coxcomb, Maccaroni(sic), Fribble and more.

The metrosexual of the Regency era.

Merriam-Webster

A man who gives exaggerated attention to personal appearance.

Wikipedia

A dandy is a man who rejects bourgeois values, devotes particular attention to his physical appearance, refines his language, and cultivates his hobbies. A dandy’s mere existence is a reproach to the responsible citizen of the middle class: épater le bourgeois in the words of Charles Baudelaire. A dandy emulates aristocratic values, often without being an aristocrat himself, thus such a dandy is a form of snob. A dandy was differentiated from a fop in that the dandy’s dress was more refined and sober.

1811 Vulgar Tongue

dandy –That’s the dandy; i.e. the ton, the clever thing; an expression of similar import to “That’s the barber.”
dandy prat — An insignificant or trifling fellow.

Bucks are men about town. Perhaps in lieu of a better example, you could consider bucks the classic frat boys of the Regency era.

1811 Vulgar Tongue

Buck — A blind horse; also a gay debauchee.
A Buck of the First Head — One who in debauchery surpasses the rest of his companions, a blood or choice spirit. There are in London divers lodges or societies of Bucks, formed in imitation of the Free Masons: one was held at the Rose, in Monkwell-street, about the year 1705. The president is styled the Grand Buck. A buck sometimes signifies a cuckold.

Merriam-Webster

A male human being : man : a dashing fellow : dandy

(It is interesting to see dandy used in the definition. In many Regency set novels you will not see the terms used together! More on dandies next week…)

Usually used in positive terms in novels — often as a younger man with good fashion sense and charm. That really hot guy in high school that cut a dashing figure and all the ladies swooned over? Definitely a blade.

Merriam-Webster

A dashing lively man.

Oftentimes used for the “mischievous charisma” definition.

Merriam-Webster

A dishonest or worthless person : scoundrel
A mischievous person : scamp

Wiktionary

A scoundrel, rascal or unprincipled, deceitful, and unreliable person
A mischievous scamp

Roguish — 1. A mischievous charisma. 2. Unreliable or self-serving. 3. Wandering or appearing randomly.

Corinthians are usually shown as the fashionable sportsmen of the Regency period. In novels, they are often depicted in exclusive groups, sometimes as debauched and uppity fellows. However, other times they are referred to in a more positive manner — handsome, sporting and dashing. Today the term is used for the spirit of amateur sports.

1811 Vulgar Tongue

Frequenters of brothels. Also an impudent, brazen-faced fellow, perhaps from the Corinthian brass.

Merriam-Webster

A merry profligate man

Alternatively rakehell or rakeshame. A negative description for a man of questionable morals.

The favored term for a hero knowledgable in the bedroom, with a string of ladies in his past. Many Regency novel heroes are “fake rakes” or deemed by the general populace to be sleeping with women left and right, but not philanderers in reality. Or they have all the good qualities of a rake (ie. they know what they are doing behind closed doors) but few or none of the bad ones (e.g. uncaring, debauched, dissolute, etc.). A rakish hero could refer to a man who cares little about what others think and freely takes as he pleases, or one who simply looks rakish — he has a wicked gleam in his eyes and a cat-like, prowling grace. Romance writers take literary license with this term, and really who can resist the rakish hero as defined by Regency romance?

1811 Vulgar Tongue

A lewd, debauched fellow.

Merriam-Webster

A dissolute person : libertine

Wikipedia

A man habituated to immoral conduct : roué