says...

Duplication

With great power comes great responsibility. Imitation, mimicry, duplication, copying – these are the most useful power. Why is this useful? You ask. Well, duplication is useful because it could help people and yourself in any matter.  Picture the scene: “You’re trapped in a cave connected to a volcano which is about to erupt”. What will you do? A genius like myself would for example mimic the power of invincibility (which means I can’t get harmed by the lava) this is not enough alone I will then use the power of animals and turn in to a dragon and swim my way out and fly away.  

What power is the least useful? I think strength is the least useful because there are different powers that could be useful in the same instance as strength (like the power of smoke or the power to change size).

I also think the power of love is one of the least useful because it could cause distraction to your teammate.