Yes, the US civil service was very corrupt by the late 19th century. Andrew Jackson started the practice of awarding jobs in the federal government to supporters of politicians who won elections in what is known as the spoilage system. The result is that civil servants were not chosen on the basis of merit but rather on the basis of political loyalties and the civil service was filled by politicians assigning cushy jobs to their friends. Throughout the 19th century the spoilage system was standard tactic for ensuring political support during elections and as a result the civil service was very corrupt.

This changed in 1881 with the assassination of president James A Garfield by a frustrated office seeker who believed that he was promised the post of ambassador to France and was angry that he didn't receive the job. The resulting public outcry, fueled in part by a growing middle class who are frustrated by inability to acquire positions given out by the spoilage system despite their superior technical education, forced the government to reform the civil service. Congress passed the Pendleton Civil Service Reform Act of 1883 banned handing out offices on the basis of political affiliation and established an examination system as means of determining who got jobs in the civil service. The net result is that office holding became to a much larger degree based on merit rather than connections and the civil service stopped being an institution for rent-seeking.

Source: Political Order and Political Decay by Francis Fukyama

Yes. Under the long stewardship of Lew Kuan Yoo, Singapore dramatically transformed in many ways, including a reduction in corruption.

By simultaneously increasing the salaries for Singapore's officials and making the sentences for corruption harsher, Singapore brought the corruption levels down to among the lowest in the world.

A recent article in The New Yorker summarized it:

By the time Lee stepped down as Prime Minister, in 1990, Singapore had gone from being one of the more corrupt countries on the planet to one of the least. According to Transparency International’s most recent Corruption Perceptions Index, Singapore now ranks seventh in the world for transparent government—less corrupt than Australia, Iceland, or (by a good margin) the United States.

It's probably also worth noting that the same article stressed how rare and challenging it is to remove entrenched corruption, and the difficulty of implementing Singapore's carrot/stick approach elsewhere:

It might be tempting to extrapolate lessons from a country like Singapore, but Singapore is a tricky analogy for Afghanistan. With just over five million people in a territory of less than three hundred square miles, Singapore is tiny, centrally controlled, peaceful—and rich. And it is not just corruption that has been abolished on the little island but a variety of lesser human infractions, from spitting on the sidewalk to failing to flush a public toilet: the population is subject to an authoritarian penal code. Most important, perhaps, Singapore had, in Lee Kuan Yew, a leader who was truly invested in the anticorruption agenda.

Source: "Corruption and Revolt." The New Yorker. January 19, 2015.

Great Britain had a lot of corruption in the late 1700s. Not just pocket boroughs; members of parliament were receiving sinecures and places, naval procurement was corrupt, and reversions could allow succession of relatives. Reforms were very gradual through the 1800s.

The KMT were notorious for corruption when they fled mainland China. Now, per http://www.transparency.org/cpi2014/infographic/regional/asia-pacific , Taiwan is not New Zealand, but it's not Pakistan either.

Many reforms came about that were nonviolent or at least not part of some larger revolution. Just in the United States you have the examples from the progressive era that while might have involved many violent incidents such as strikes you had the increase of working conditions and regulations simply from more awareness and government intervention. Passing a constitutional amendment for the direct election of senators could also be seen as an example as could the opening up of the political party primary system over the 20th century

On a smaller scale you can look to Tammany Hall and how it went from a cesspool of corruption to a waning influence that eventually dried up. For an overview of how it began to lose power I'd look at Franklin Delano Roosevelt and Tammany Hall of New York by Charles LaCerra

Czechoslovakia had revolution without firing bullet in 17.11.1989 .