The idea of loyalty is broad, and encompasses things as different as patriotism and staying faithful in a committed relationship. Most people would agree that loyalty is a positive and desirable character trait, and that it should be a part of everyone's character development. Loyalty cannot exist in a vacuum though. People are often loyal to corrupt dictatorships, for example, and so other positive traits are needed.
Honesty is another important character trait that is well worth taking the time to fully develop. According to the "Stanford Encyclopedia of Philosophy" an honest person is someone who is honest in their dealings with others and also discourages the dishonesty of others. In other words, it is not enough to avoid lying to other people, to be an honest person you must strive to have integrity in your dealings with others.
Wisdom is another broad character trait often associated with the process of character development. Wisdom is often equated with intelligence, but it represents much more than that. It is the accumulation of knowledge and insight as well as the reason and judgment necessary to apply and make the most of that knowledge and insight. Socrates famously said that "I know that I know nothing," which is taken to mean that Socrates had wisdom enough to know that nothing could be known with absolute certainty, which is a humble sort of wisdom.
Courage is another very desirable character trait that anyone embarking on a character development program should consider. There is physical courage, which is the ability to withstand and overcome pain, physical limitations or even the threat of death. There is also moral courage, which is the ability to adhere to your own beliefs and morals even when it is inconvenient or unpopular to do so.