as they say nothing is impossible hey? just is it probable?
you would need a very strong anchor point on the opposite side of the
lean and then a block and tackle so you can keep adding pressure to
maybe make the tree come back straight. the top will of course now
grow straight now that the other tree has gone. doing this with
younger trees is a whole lot more doable.
if it where me i'd write this one off and relegate it to mulch or the
fire place and plant another.
With peace and brightest of blessings,
"Be Content With What You Have And
May You Find Serenity and Tranquillity In
A World That You May Not Understand."