Should a Champion attempt to avenge all his defeats?

Yes, but only if it's viable and relevant. No use in having a world champion proving himself against a journeyman that may have gotten a nod over him early in their careers.

 

I think Pac should avenge his losses to Medgoen Singsurat and Rustico Torrecampo.

 

I always thought so.

 

Only if there is no better and younger opponent willing to take the fight.

 

if he's still considered a top fighter, yes.