As the other educator already mentioned, Sir Thomas More had many achievements. Let's look at two in depth.
In life, Sir Thomas More was an important scholar and author. He was a peer of the theologian, Erasmus. He also wrote against Martin Luther and the Reformation. Most notably, however, he wrote The History of Richard III, which most consider to be the first historiography. This was followed by his book, Utopia, a fictional account of a republic ruled by reason, not exactly the world he lived in!
In death, Sir Thomas More achieved what many would consider the most significant title anyone can, saint. Although More was executed for treason in 1535, the Catholic Church canonized (AKA sainted) him in 1935.
"He has also been deemed a "Reformation martyr" by the Church of England" (biography.com).
More was found guilty of treason because he had not supported King Henry VIII's rebellion against the Catholic Church nor did he support his attempt to divorce Catherine of Aragon. It is appropriate, then, that the Catholic Church acknowledged his devotion by finally canonizing him.