Assassination was the act of killing an important individual for political or ideological purposes. Those who carried out assassinations were known as assassins, who may have been in the employ of a government or other group, or operated independently for hire.
By 2366, Dukat had survived four assassination attempts during his time as Prefect of Bajor. Timor Landi, Ishan Chaye and Jillur Gueta were executed for an attempt in that year. (DS9: "Things Past", "Waltz")
The same year, a Bajoran officer tried to assassinate Commander Benjamin Sisko with a small device he received from Doctor Julian Bashir. All participants were under the influence of the Saltah'na energy spheres. (DS9: "Dramatis Personae")
In 2371, Enabran Tain ordered the assassinations of several former associates, including Garak, who posed potential threats to his return to power. Garak was able to preempt his assassination attempt by the Flaxian Retaya by destroying his own shop. (DS9: "Improbable Cause", "The Die is Cast")
In 2374, the Orion Syndicate attempted to assassinate the Klingon ambassador to Farius Prime at the behest of the Dominion. The plan failed due to the actions of Miles O'Brien. (DS9: "Honor Among Thieves")
In late 2375, Luther Sloan and Section 31 duped Julian Bashir into believing they were about to assassinate Tal Shiar Chairman Koval. In reality, they hoped to stop Kimara Cretak from taking Koval's seat on the Continuing Committee. (DS9: "Inter Arma Enim Silent Leges")
In 2379, after Praetor Hiren rejected their demands by Commander Suran to forge an alliance with the Remans against the Federation, Senator Tal'aura used a thalaron radiation projector to assassinate the entire Romulan Senate. (Star Trek Nemesis)