another country when he was killed.
The other despots you name were not engaged in such activity. Thus, no, they did not meet the same definition.
I am not surprised that you are once again caught up in the tangle of definitions on this. Soleimani had a long track record of terrorist activity, he was meeting with the terrorists who had just attacked our embassy and killed a US contractor before that, and out intel said that he was actively planning another imminent hit on the US.
All Iran would have had to do to protect any terrorist is to name him a general if we were to follow your rules.
Now, you might make an argument that Trump shouldn't trust his intel community for this info since they might try to lie to him like they did to Bush, but Trump is leader, and as such was able to look beyond the IC's past transgressions.