Let me state a few things before I make my point:
TLT says to cancel all dice results after you are hit and have suffered your 1 damage.
The Harpooned! effect resolves if you are hit and then there are no uncanceled crits.
To me, it seems like the act of getting hit by the TLT necessitates in resolving the effects of the TLT card first. But regardless of how this argument resolves, it's piss poor sportsmanship to tell your opponent that you are going to use the crit that is about to be canceled as the uncanceled crit to set off the Harpooned! effect. That's just shady gameplay.