English equivalent of the Malayalam saying "don't stab/poke the dead body"?

ശവത്തിൽ കുത്തരുത് (śavattil kuttarut)

is a Malayalam saying that in literal translation means "Don't stab/poke the dead body". The meaning would be something like: don't humiliate a person when he is at the bottom end.

How about -

Rub salt into the wound

To make something that is already difficult, unpleasant, or painful even worse; to accentuate, aggravate, or intensify a negative situation, emotion, or experience (for someone).

(From The Free Dictionary)

OR

If someone or something rubs salt into the wound, they make the unpleasant situation that you are in even worse, often by reminding you of your failures or faults.

(From the Collins Dictionary)

OR (a simpler meaning)

To make a difficult situation even worse for someone

(From the Cambridge Dictionary)

"My pride was already hurting when I didn't get the job, but hearing that they gave it to Dave really rubbed salt into the wound."

"To rub salt in the wounds, the bankers got big bonuses as the rest of us struggled to make ends meet."

Perhaps

Kick someone when they are down

Cause further misfortune to someone who is already in a difficult situation.

From Oxford.

"Don't kick a man when he's down."