Why was Harry Truman so unpopular at the end of his presidency?

From about the midpoint on of his Presidency, Harry S. Truman experienced catastrophically bad approval ratings. From November 1951 to February of the following year, he registered a measly 33% approval rating from the American people, which at that time was unprecedented.
There are a number of reasons for such unpopularity. First and foremost was Truman's conduct of the Korean War. The President's Republican opponents, as well as some within his own party, criticized Truman for what they saw as an over-cautious approach to the war. Instead, they recommended a more robust, aggressive response to what they saw as the Communist threat.
Public opinion tended to side with the Republicans, especially after Truman relieved General MacArthur of his command due to irreconcilable differences between these two outsized personalities over the war's conduct. MacArthur was very popular with the American people, and so when Truman let him go, public opinion inevitably turned against the President. Though Truman's approval ratings eventually rose slightly, they never moved out of the 30s, a shockingly low figure by anyone's standards.