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. If you'd like, you may PM /u/caffarelli to have your question considered for an upcoming Tuesday Trivia thread.

When the highest percentage of people trying to, at the same time, try to harm/kill each other is a pretty impossible question to answer in some universal way. Is there a specific culture or nation or people you would specifically like to know about? Because answering what would be, say, Egypt's most violent period or Ireland's most violent period is more reasonable to quantify and answer than all of humanity across thousands of years of history.

It may be useful to resubmit with that specificity so that we can come in with a better answer.