Samuel Tilden (1814–1886) lost the disputed presidential election of 1876. He won more popular votes than his opponent, but he lost in the Electoral College after a dubious arrangement gave disputed Electoral College votes to his opponent.
Although we cannot know for certain, it is probable that Tilden would have been a competent president. His personality traits were largely positive ones: he was sagacious, honest, efficient, forgiving, and munificent.
Tilden was a sagacious lawyer who was well-paid for his work. He invested his money wisely and became wealthy, though he was never haughty in spite of his great success.
Many of his positive traits were on display during his tenure as party chairman (Democrat) and governor of New York. He fought against the corruption in the Tweed Ring and Canal Ring. His loathing of corruption could have served the nation well had he become president. Tilden had a penchant for organization and he made the Democratic party of New York much more efficient. His success in New York state brought him to the forefront as a presidential candidate in 1876.
Tilden accepted the 1876 loss without becoming bitter. (In this respect, he was not unlike Al Gore after the 2000 election.) Tilden could have rallied his supporters against the unfair outcome, but he feared the potential repercussions for the nation.
Tilden, a wealthy man, was very generous. He left a great deal of money for the establishment of the New York Public Library.