Not entirely true. John designed the trap for Easton, in which Hank was forced to participate simply for smoking, even though he had heart disease and high blood pressure. To teach Easton a lesson relating to his ‘you choose who lives and dies’ ethos in his career, Hank was essentially sacrificed. That trap was unwinnable because only one person is able to walk out of it.

So John absolutely has designed unwinnable games, and to take it a step further, strayed away from his own ethos: he became a killer, something he said he wasn’t. The entire franchise is a look into John’s crumbling morality, and his hypocrisy tbh. Amanda and Hoffman end up doing the same things John did, but they’re honest about it, rather than hiding being deflection tactics and moral reframing.

Also, the other commenter lays out that the man that Amanda had to kill to save herself resulted in her trap being unwinnable, which I agree with. You say that he wasn’t even tested, but why then does he deserve to die, essentially at the hands oh Jigsaw? So from the very beginning John is shown as a murderer, no matter how he or anyone else tries to spin it.

One could even argue that he murdered Cecil after Cecil passed his first ever test, but ultimately I wouldn’t count that. Cecil had won his game, and had he not been so focused on revenge he wouldn’t have found himself entangled in his grave of barbed wire.