When people think of Henry VIII, they think of a cruel tyrant who savagely executed those whom he opposed for treason, particularly his wives. It would behoove us all to remember that Henry was, above anything else, a human being.
To really understand his actions, one must look at the beginning of his life. Henry VIII was born in the aftermath of a civil war in which Yorkist and Lancastrian factions battled for control of the crown. In the end, Henry's father, Henry VII, a Lancastrian, became King of England. At the time of Henry's birth, there were a large number of people (mainly Yorkists) who didn't recognize his father as the true king, but rather saw him a usurper.
Furthermore, Henry was the second child when he was born. His brother Arthur was the one who was destined to be king; it was Arthur who was first married to Catherine of Aragon. However, fate had a different mind for Henry when Arthur was struck down by the sweating sickness. Henry, now heir to the throne, was promptly married to his widowed sister-in-law.
Since he was never meant to be king, it could be assumed that, naturally, he was already in a defensive position when he came to the crown. It's not difficult to imagine that he was probably very determined that his subjects recognize him as their true king, as opposed to a usurper, like his father.
Examples of Henry's cruelty are present very early in his reign, however. Almost immediately after his coronation, he had Sir Richard Empson and Edmund Dudley arrested. While the pair were unpopular, the charges of treason lain against them were baseless. They were executed and stood as an example for what would happen to those who dared to oppose the king.
It seems, however, that there was a point in time when Henry's anger became less political and more personal. Henry was initially on very friendly terms with Sir Thomas More to the point that it might be said that he and More were actually friends. However, coldness grew between them as Henry became more radical in his distaste for papal authority in regards to his marriage to Catherine of Aragon. Later, after More refused to take an oath regarding Henry's marriage to Anne Boleyn, Henry had him executed on grounds of high treason, killing a man who was, at one point, one of his greatest supporters. More than that, Sir Thomas More had been his friend.
One of the quickest ways to the axe was to threaten Henry's position as king. When his younger sister, Mary, ran off and married Charles Brandon, Henry was livid. It was considered a treasonous offense for a royal to marry without the king's permission. Brandon, the Duke of Suffolk, could have easily been executed for the illicit marriage. At the time, many of Henry's ministers urged Henry to deal harshly with Suffolk. However, perhaps out of filial love for his sister, Henry's temper cooled slightly. The two were sent away from court and made to pay a very heavy fine to the crown.
In regards to his cruelty, Henry is most remembered for the way in which he treated his wives. It's commonly misunderstood that all of Henry's wives suffered the axe, however only two bore the terrible fate: Anne Boleyn and her cousin, Catherine Howard.
It might be considered astonishing that Catherine of Aragon was merely divorced in light of the fact that she never produced a son. However, Henry viewed Catherine of Aragon very differently than he viewed Anne Boleyn and Catherine Howard. The latter two were Henry's own subjects; not only were they his wives, but they were women of his country. Catherine of Aragon, on the other hand, was the daughter of Ferdinand and Isabella of Spain. She was a foreigner whose nephew was the Holy Roman Emperor. To harm her in anyway could potentially mean a war that Henry would be unlikely to win.
Aside of that, it must be understood that, at the end of their marriage, Henry viewed Catherine of Aragon as a sister. After all, she had been married to his brother, which was one of the main reasons he used in divorcing her. Furthermore, Catherine of Aragon and Henry were married for a long time; they came of age together. Even though she didn't give him sons, it's likely that she held a somewhat sentimental place in his heart.
As for the two wives who were executed, Anne Boleyn and Catherine Howard, in Henry's mind, they more than deserved it.
Throughout his time with Anne, it became more than obvious to Henry that he was just a pawn in the Boleyn family game. Naturally, that offended him; as king, he should be nobody's pawn. It was under Anne's influence that Henry did things that were viewed by contemporaries as shocking. It was during her time that his trusted advisors and friends, Cardinal Wolsey and Sir Thomas More, fell from Henry's grace. Furthermore, it was due to his desire to marry her that he broke from the Roman Church. As a staunch and faithful Catholic, that was something that Henry, most likely, felt guilty about until the end of his days.
On top of it all, Anne failed to produce a son for Henry. Like Catherine of Aragon before her, she only gave him one surviving daughter. It's easy to imagine how Henry felt. Most likely, he felt like everything he did for Anne was all for naught.
Catherine Howard, on the other hand, was brazenly unfaithful to Henry. Without modern paternity tests, an unfaithful wife was a very dangerous thing for Henry. Per Catherine Howard's cheating, there was a strong possibility that any child she produced would not be Henry's; thus, it was a treasonable offense to have an affair while married to the king.
In the case of Catherine Howard, it's likely that Henry felt as though he was protecting his crown.
In later years, Henry VIII began to settle down - - particularly after his son by Jane Seymour, Edward, survived infancy. And there's a very good reason for that: with young Edward alive, Henry most likely felt secure for the first time in his entire life.
It's true that Henry VIII had a towering temper and that lives were unjustly lost during his reign. However, we must remember that most of what he did was, in his opinion, out of protection for himself and his dynasty.