Of the Sanin. Tsunade's the most physically strong of the three but I wouldn't put her as a better fighter. I guess it would be between Orochimaru and Jiraiya. I don't want to count Edo Tensei, because that's not really Orochimaru himself fighting it's him calling dead zombies to fight for him. He's not even calling the shots with the zombies really. Jiraiya has Sage Mode and was very powerful with it. He managed to defeat three of the Pain dolls without the info on their abilities that Naruto had and it took all six of them to kill him. Orochimaru's best achievements sadly have been through Edo Tensei. Without Edo Tensei he would not have been able to beat Hiruzen the way he did. Itachi doesn't fear Orochimaru at all but he is weary of Jiraiya. It's hard to determine who I would rank more powerful. Orochimaru and Tsunade both have the cheap regenerating power allowing them to survive things that would normally kill a regular person, and Jiraiya does not have that. Darn, I can't decide who would be more powerful.
Parena or Serecham both equal Serena+Pancham!