@skorned, I’ve been in the working world for a long time and listened to an awful lot of announcements of awards, promotions, thanks for service, etc., etc. I could have gone on and on. What’s hard is to say anything that sounds (a) fresh and (b) sincere. Good luck.
But…if you are not trying to praise a specific person but instead speaking about the qualities of a leader, that is a different thing altogether. In that case you must think about what it actually takes to inspire and motivate others. An interesting concept is that of the servant-leader. On the other hand, there is the view of Machiavelli, who wrote that a leader (a prince) will want to be both loved and feared, but if he cannot do both, then it is safer to be feared.
If you are trying to define the quality of leadership, you need more than a list of adjectives. You need to think about how true leaders transform the minds and actions of their followers.
If this is a homework assignment, I’m afraid that’s all the help we can give you.