Petra
Petra Arkanian was a little young girl a little bit older then Ender. Ender and Petra met each other when Ender was put into the Salamander army. Petra also taught Ender in battling like shooting. "No, just a brilliant and talented polygot. Petra Arkanian. The only girl in Salamander Army."(Page 75). This means that Petra has great strength and skilol especially for a girl. Later Petra was put in Phoenix Army for showing great strength and potential.
Petra not only has great strength but also great shooting skills "I bunk in the front because I'm the best sharpshooter in salamander Army, and because Bonzo is afraid I'll start a revolution if the toon leader's don't keep an eye on me."(Page 78) This tells that shes not only a excellent shooter but very dangerous in battle
You may think Petra is always serious but she also has a funny or humerous at some times. She told ender one time before practicing ,"'Come, little boy, the battle-room is ready. Petra's hands are steady. The enemy is deadly.'she giggled."(Page 83). This shows us she has fun while battling and enjoys it.