That depends on your definition of democracy, not to mention of "no violence". As to the latter, to take an extreme case, if a new type of government comes to power, and in the course of it two drunks in a bar have an argument about whether the new government is better than the old and they throw a couple of punches, and that is the only violence, would you say that that means it failed the "no violence" test? I'd say absolute zero violence is probably almost impossible.
That said: Rome turned from a republic to a dictatorship with relatively little violence. Yes, there were a series of civil wars, but those wars took place under the republic. It's a common analysis to say that the people accepted the dictatorship because they believed a strong enough government could end the civil wars.
Western Europe and he US are drifting from democracies to rule by an unelected elite with very little violence.
Ancient Israel went from a rather libertarian society to a monarchy with no apparent violence. In that case the people generally favored it because they believed a king could better maintain a standing army to protect them from foreign invasion.
** Further thought **
The Roman Empire was probably a bad example. There was fighting by the Republicans under Brutus against the Imperialists under Augustus. Duh, forgetting my Shakespeare, even.
But a much better example hit me, an absolute classic example: Nazi Germany. Hitler came to power through free elections and political maneuvering. Then of course once in power he took steps to make it impossible for him to be voted out of power.
The Nazis did try to overthrow the government by force -- the "Beer Hall Putsch" -- but this failed. They then switched to using legal means.