Germany is perhaps most favored to be 'the bad guy' in any World War, not because Germans are innately evil or ambitious or something but for deeper, larger reasons. Let's look at this like we are solving a mystery. Our crime is World War while 'being Evil'. (While this is of course a judgement call, we can guess our any TL might judge a power.). Let us examine Method, Opportunity, Motive for Germany and see why it is so special (and what other nation or power can take its place).
Method: We can scratch most nations for simply lacking the means to fight in a World War. While our culprit doesn't need to fight alone, a Bad Guy should be a super power strong enough to fight off a horde of foes. An evil 'alliance' doesn't really work or make sense. Germany is a heavily industrialized nation right in the heart of Europe, the hotbed of technological capability in the time period we are interested in. With a highly industrial economy, excellent educational system and talented bureaucracy Germany can, under many kinds of leadership fight powers many times its size. Also, it has a long and well regarded military tradition going back to Frederick the Great or farther. this is not very rare of course (everyone from France to Russia or Turkey has this) but it would be foolish to ignore the very real martial strain Prussia gave Germany. Germany also, under many regimes, has the will for war (like most n nations). Germany certainly has the means to fight a World War with a hope of winning.
Opportunity: A World War is a feature of only a limited time frame in the early Second Industrial Revolution. While thee have been global wars before (The Seven years War comes to mind), what we generally consider a World War seems to require mass industrialization, total war and a truly global set of threats and circumstances. Unlike many nations Germany is coming to age at exactly the same time. In many ways Germany is a child of both nationalism and industrialization (much like the USA, actually). Germany is also uniquely placed to fight such a World War. Unlike say, Japan, it is located at the very center of European (and in this time period world) politics. Nearly every border is/was located directly against another Great Power, creating a zero-sum situation on nearly every front. Germany is in exactly the right place at the right time. Any earlier and a nation (say Mughal India or Ottoman Empire) lacks the economic/technological means as well as ideological imperative for World War but any later (say modern South Korea or Brazil) and the landscape has sharply turned away from World War.
Motive: Due to the above, Germany is also given a motive. By its very nature, it's rise to power and 'place in the sun' is in direct opposition to the already situated Great powers. Germany is outside, looking in, at the already established empires and nation. It is placed outside the system and wishes to upset it (or at least severely alter it to suit their own needs). Few other nations see a fundamental re-altering of the landscape as required, which is what is required for a World War.
