Dan Carlin enjoys these kinds of comparison, but there is simply no way to quantify the "worst" battlefield. This question also almost certainly would violate the "across all eras" rule for questions on this sub, I'm sorry to say. You can read the rules here: http://www.reddit.com/r/AskHistorians/wiki/rules

This submission has been removed because it violates the rule on poll-type questions. These poll-type questions do not lend themselves to answers with a firm foundation in sources and research, and the resulting threads usually turn into monsters with enormous speculation and little focussed discussion. “Most”, “least”, "best" and "worst" questions usually lead to vague, subjective, and speculative answers.