For Odysseus, if he didn't have the trust in his men then, he would not be as well known, powerful in wealth, and he would have been sent to defeat Troy. Not only did he have the trust of his men, Circes did also. If he didn't Circes wouldn't have taken the time to explain and give advice to him. (Book 12, description on top)
For Tatsuya, although at the beginning of the series he was thought of not so intelligent or helpful in his magic use, he later on one okf the most trusted people that, the student council, relies on.