There's a command to do it, it's named rev
from util-linux :
$ rev file
d c b a
f e
i h g
or using perl :
$ perl -lane 'print join " ", reverse @F' file
d c b a
f e
i h g
But like you explain in the comments, if you want the 3 latest columns, you can use awk :
awk '{print $(NF-2), $(NF-1), $NF}' file