Sakura is very strong and a good healer especially in the shippuden arc, but I still worry about her emotional instability. Lol that sounds weird but, she always turned into such a goof around Sasuke, and ignored reason, so I'll hold back judgement of best kunoichi on her until I see if she's gotten better. I get that she loves him, but she doesn't have to squeal . . .
Lol who am I to talk, though? I think Tsunade should win the title for now, just because she can summon a slug that's the same size as a biju. Granted, slugs are yucky, but the power is cool.