
I like to point to this page from Franquin's Idées Noires (finally in English as "Die Laughing", only a few decades late) [1], which makes much the same point as you. (The whole book is very much worth it if you like dark humour - it's a crime it took so long for it to get translated to English given how many other languages it's been translated to decades ago)
Translated the speech bubbles are roughly:
"The law is clear: Every person who voluntarily kills another will have their head cut off. Let the executioner do their job."
"Over here, my friend."
"And so a good deed done..."
"Sorry, but the law is clear: Everyone who voluntarily kills another..."
[1] https://i.pinimg.com/474x/c5/3c/45/c53c451e1fea4fd04ea6cf674...
A rough translation (my French is rusty - been a decade or two): "The law is clear: Anyone who intentionally kills another will lose their head. Let the executioner do his duty." "This way, my friend" "And so, a good deed done" "I'm sorry, but anyone who intentionally kills another..."
(Idées Noires is fantastic and macabre. Franquin kept "letting" people who causes suffering for other people - or animals - die horrible deaths in his panels, often with a solid dose of poetic justice in between other things, and coupled with rather caustic political commentary. Unfortunately, AFAIK I don't think there is an English translation (one was in the works), but even with quite modest French they're relatively easy to understand (many of them don't have much or any text))
[1] http://www.franquin.com/in/album3_in.php - rightmost panel on the top.
Like you, I enjoy Gaston significantly more than Spirou; he also has a more adult work called Idées noires (Dark Thoughts), which is filled with great (and often disturbing) dark humor. It's probably not translated to English either, alas.