What if I said that I lied to a suicidal person?
Why did you lie to a suicidal person?
I thought it was funny and wouldn't cause them any harm.
I understand that you thought it would be funny to lie to this person, but that lie could be very damaging. Lying to someone that's in such a fragile mental state could cause them further harm. You cannot truly understand the ramifications of the lie for this person.
I'm going to destroy their life and make them look weak.
Why would you intentionally hurt them? You should never harm someone just to satisfy yourself. You should be helping out this suicidal person instead.