Use 'unreservedly' when you want to give a strong, confident recommendation without any doubts. She unreservedly endorsed the candidate for mayor.
Pro Tip 2/3
Total Acknowledgment
Use it to show you fully acknowledge something without denial or evasion. The company unreservedly admits that its product caused inconvenience to customers.
Pro Tip 3/3
Sincere Apology
When saying sorry, 'unreservedly' conveys a sincere and complete apology. I unreservedly apologize for the mistake that was made.