How to level columns in bibliography?

You can use balance package. Put

\usepackage{balance}

in the preamble. Then, somewhere in the first column of the last page, put

\balance

Following is a screen shot from the manual of balance package.

Disclaimer: This solution may work depending on your class and bibliography style or (worst) may not work. To have an accurate answer, pl provide a MWE.

You can use the flushend package. Just add

\usepackage{flushend}

in your preamble. It will then take care of the balancing for you. There is no need to add a special macro on the final page of the document.