As AI171 has shown, turning the engines off on rotation does it reliably and there’s nothing that the other pilot or regulations can do to prevent it.
I wonder of such regulations are in fact counterproductive if it means people don't seek out help when they can and let the problem escalate instead (since you presumably don't go from healthy to murder-suicidal in one day, and early intervention could resolve the problem).
Air travel is weird in the sense that pilots do have an immense amount of power and the fact that there have been so few pilot suicide cases shows that regulations for that are somewhat working.
Indeed I wonder how much of aviation-related security theatre is more for the perception of safety than any measurable safety improvements.
> there have been so few pilot suicide cases
I'm not sure it's conclusively possible to attribute this to regulations without a "control case" of a different profession lacking such regulations and that has a higher rate of murder-suicide-by-vehicle. It could just be that the low rates are because there just aren't that many suicidal people willing to kill innocent bystanders in the process.
To be clear I'm not arguing for less regulations as I'm not qualified and don't have all the facts, but bringing up a counterpoint that the current regulations might cause people to conceal their mental health troubles until they escalate (and the current low - but non-zero - rates of incidents are in spite of the regulations rather than because).