Phyrexian Splicer

{2}, {T}, Choose flying, first strike, trample, or shadow: Until end of turn, target creature with the chosen ability loses it and another target creature gains it.

The List

Tempest

o2, oc
T: Choose flying, first strike, trample, or shadow. Target creature with that ability loses it until end of turn. Another target creature gains that ability until end of turn.

If the target which is having the ability removed does not have that ability during the resolution of this effect, then this effect still grants the chosen ability. The reason is that the second target is still legal even if the first one is not.