The phrase "big congratulations" is used to express a very positive and sincere recognition or praise towards someone's achievement or success. Full definition
Big Congratulations on just the possibility but even bigger Congrats because It will happen! (theletteredcottage.net)
Big congratulations go to the winners of the first Great British Make Off, as well as a big thank you to all the students, teachers and schools who entered this exciting competition. (educationbusinessuk.net)
If you have recently had a baby too big congratulations! (naptimenatter.com)