Qfyilyi

In other words, an idiom for empowering someone with a capability that they might, through ignorance, misuse to self-detrimental effect.

The motivation for an alternative is the professional setting, where it's not appropriate to allude to suicide!

Perhaps something like letting one "dig their own grave." Hope this helps.

Well, to be nice to new contributors, here is a genuine suggestion:

Bite off more than he can chew

(unless the act of chewing is considered vulgar with its association with gum).

For a strict analogy to “Give him…” you would need to make this something like “Have him bite off…” or “Make him bite off…”.

[But I do think that we use many phases without thinking about the original meaning of the words — a killing look, dead beautiful, kick the bucket (death by hanging), dig your own grave, annihilate, wipe out (skiing terminology) etc. etc.]

More of a phrase than an idiom, but...

set someone up to fail / set someone up for failure

From Wikipedia (I know, I know... but it's the best source I could find):

Setting up to fail is a well-established workplace bullying tactic.[6][7][8] One technique is to overload with work, while denying the victim the authority to handle it and over-interfering;[9] another is the withholding of the information necessary to succeed.[10]

If a person puts another individual (usually a subordinate) in a
stressful situation in which failure is almost certain, this may be an
aspect of bullying wherein the outcome can then be used to discredit
and blame the victim.[11] Sometimes, this may involve the bully
covertly sabotaging and undermining an objective that may have
otherwise been achievable. This type of bullying may be the result of
the projection of the bully's own feelings of inadequacy onto the
victim.[12]

There can be cases where an employee is set up to fail because the
stated goals of the task are considered harmful to the organization;
an internal investigation is one example. Institutions may protect
themselves by "going through the motions" of a sham investigation in
which the findings conveniently fail to find any evidence of
wrongdoing by the authorities involved with setting up the
investigation.

From the Harvard Business Review:

That was specifically about employees and bosses, but it's possible for parents/children, co-workers, teammates... any number of relationships. Even yourself!