Let's try to get the logic of this... shall we?

[Scaletho]

I must kill a person, but I'm FORBIDDEN to perform the mission with ANY casualties... no way I'm allowed of dealing lethal damage.
Ok, no problem! I just switch my weapons to stun and bring Solange... wait, what???

 

[Frop]

That's just the wording that's confusing. If you only kill the mission target, you'll be fine.

 

[Imran Hazard]

You get these assassination missions in ship as well, there the concept is called "clean kill"

 

[Bottom Hat]

You get these assassination missions in ship as well, there the concept is called "clean kill"

You're right - the "clean kill bonus" in horizons missions means not going to the rebuy screen.


Edit - I presume it's the same here

 

[The Roofus]

Maybe you're supposed to give them a fate worse than death?

Like, offering them an all expenses paid trip to Swindon.

 

[Drelthar]

Maybe you're supposed to give them a fate worse than death?

Like, offering them an all expenses paid trip to Swindon.

You monster

 

[Northpin]

I must kill a person, but I'm FORBIDDEN to perform the mission with ANY casualties... no way I'm allowed of dealing lethal damage.
Ok, no problem! I just switch my weapons to stun and bring Solange... wait, what???
View attachment 256705

As been pointed out, you only need to kill your designated target. IF you kill anyone else, you will fail the mission.

 

[Bottom Hat]

Maybe you're supposed to give them a fate worse than death?

Like, offering them an all expenses paid trip to Swindon.

You monster

Oh my, that is an awful thing to suggest....

Still, at least you didn't suggest the eighth circle of hell, which can be seen in Dante's Inferno, and now going by the name Milton Keynes.