Who was the worst colonizer?

Looking at the current conditions of former colonies and some of the aggressions committed by the colonizer, which country would you say was the worst?

At present, I believe that Britain was the best and Belgium was the worst. The main reason is the relative economic strength, peace and freedoms found in the former British colonies. The US, Canada, Australia, New Zealand and, to a lesser degree, South Africa are among the most prosperous countries on earth. And even the conditions of countries like Kenya, Tanzania, Zambia, Zimbabwe (up 'til recently), Nigeria etc. are much better than those of there French, Portuguese and Belgian counter parts.

As for the Belgians, their former colonies are the Democratic Republic of the Congo (formerly Zaire), Rwanda and Burundi. Each is among the most war torn, unstable and poorest countries on earth... not to mention the horrible exploitation under Leopold's rule.

(Note: Tanzania, Rwanda and Burundi were German until WWI)

Thanks!