Defense vs. Offense
If you provide arms to a country, you can claim it was for purely defensive purposes, which is considered a valid right by every nation (and certainly every nation with a military).
If you provide a bounty for the death of particular individuals, then you are saying: "Our interests are not naturally aligned, but I will align them by proffering a financial incentive." If the targets needed to be eliminated to secure the country, then no bounty should be required. The money says: "Those people don't need to die to make your country secure. They need to die because I want them dead." This is literally "contract killing", and no country's legal system allows that as a matter of course.
Thus, we see that the CIA offering weapons to the Afghan Mujahideen is not contract killing, because the CIA didn't need to tell the Mujahideen to target anyone in particular. However the Afghan Mujahideen chose to use the weapons was more or less aligned with the CIA's interests.
While the CIA has been involved in coups all around the world, they primarily worked with actors that had aligned interests. So, without condoning its behavior, it is fair to say that as far as we know, the CIA has not needed to compel lethal action via direct financial incentives. It has largely been sufficient to provide weapons, transport, and logistics to actors who are already internally motivated to work towards a particular outcome.
Perhaps the closest American case would be that of the failed 2020 Venezuela coup attempt. In this case, mercenaries were allegedly contracted by the Guaidó administration-in-exile (for lack of a better term). However, in the end, it is presumed that the ill-fated operation proceeded because of the $15 million bounty on Maduro placed by the US government. Technically, the bounty is for information leading to the arrest of Maduro, not his assassination. However, one can presume that actually handing over Maduro in handcuffs would also qualify. Presumably, handing over Maduro in a body bag would not, since the US does not have provisions for arresting dead bodies.