Leonard McCoy (mirror)

In the mirror universe, Doctor Leonard H. McCoy (2227-2269) was a $𝜇$ Starfleet officer who served as Chief Medical Officer aboard the in the 2260s.

His sickbay was filled with torture devices that appalled his primary universe counterpart.

So alike were the actions of the two McCoys that they both spilled acid on tables in their respective sickbays, creating a duplicate burn mark on each.

In 2266, McCoy spilled acid on a lab table in sickbay. In contrast to the primary universe, the stain was not cleaned and remained until at least another year.

In 2267, Dr. McCoy accompanied a landing party consisting of Captain $𝜇$, Lieutenant Commander $𝜇$, and Lieutenant $𝜇$ to the surface of the planet Halka to demand that the Halkans hand over their dilithium crystals to the Terran Empire. When the party were beamed back to the Enterprise, an electric storm caused the party to transpose with their primary universe counterparts. However, the landing party were later put back into their correct reality.

After the landing parties returned to their respective universes, the Spock of the primary universe told his Dr. McCoy and Captain James T. Kirk that he found their counterparts to be "brutal, unprincipled, uncivilized, treacherous; in every way splendid examples of Homo sapiens, the very flower of Humanity." 

Mirror Universe Trilogy
In one permutation of the mirror universe, Dr. McCoy was hanged outside Starfleet headquarters in 2267 along with $𝜇$, $𝜇$, $𝜇$, $𝜇$, $𝜇$ and $𝜇$. 

Star Trek: Mirror Universe
McCoy's predecessor as the Enterprise's chief medical officer was $𝜇$. (SS TOS (The Greater Good))

On the orders of the Empire, he tortured his father $𝜇$ to death at some point prior to 2267.

In the months following $𝜇$'s assassination of Captain Kirk, McCoy became more and more suspicious of the actions that Spock was taking, such as persuading Troyius and Elas to become allies, which violated orders from the Empire. Lieutenant Commander Scott and Lieutenant Uhura shared his concerns and together they plotted to remove Spock from command of the Enterprise. However, as Uhura began to carry out their plan, she was disintegrated by the Tantalus field, and McCoy's criticisms were silenced.

McCoy eventually died in 2269 of the fatal disease known as xenopolycythemia, indicating that in the mirror universe, either the Enterprise crew never encountered Yonada, or they simply destroyed the vessel. He was succeeded as the Enterprise's chief medical officer by $𝜇$, who continued to serve in that position until at least 2287.