Treat others the way you want to be treated. Show compassion, empathy, understanding and support. Now, this doesn’t mean be a softy all the time and let others take advantage of your kindness, but it means don’t go out of your way to make lives of others miserable and unnecessarily difficult.
As a leader, one of your primary responsibilities is to make lives of others better, easier and as such one should never get down to the level of vindictiveness, pettiness and resentment. Rise above personal attacks, character defamation and focus on solutions and how to achieve them collaboratively. Everyone needs to work together towards common goals, vision and that can only be achieved with mutual respect, support and collaboration.