ABSOLUTELY NOT. basically, the definition "execute" means that it scales on enemy missing health so that ability should only be used to, well, execute the enemy as it then unfolds its full potential.
tho since basically all abilities that deal high single target damage are classified "executes" by the LCS casters and rito, i would say just fuck that concept alltogether. having indicators for that just makes it way too easy. could just make it so that if you are near a champion you can kill with one of your target-spells, you automatically cast it.