nihilus,is what i vote for...just pure emptiness and death,nihlius wins automatically. Hes a breach in the force and knows no end to his inescapable power and hunger,his hunger is never satiated.
I only mentioned plageuis because he is very rare,able to save otehrs from dying and can creat life,i dont have an intenetion for him to live,and now it seems anakin is the lead.
Perhapes anakin is a far better choice,now against plageius no,maybe nihilus,its not enough for the hunger to stop a infinte power of anakin. Plageieus would certainly be outmatched,due to his lack of focus in other necessary powers,like lightning or such.
Since anakin is the chosen one,he would be uber powerful at thirty,but only if he isnt a machine.
how can this be a fair pairing off, not much is known about plagueis, if at all. the best you could go on is that plagueis had the ability to keep the ones he loved and himself from harm (as palpatine said to anakin in Ep3).
in that respect, plagueis could fair well against nihilus...im not really well knowledged about nihilus, so i couldnt defend him...