“An asset” is a great formal synonym you can use. “Asset” is used in business English to refer to anyone (or anything) that is useful for one reason or another. You can use it here … See more

“A huge help” is a slightly more informal synonym. It works well because it shows that someone was willing to put time into helping you or the team out. “Huge” is the modifier he… See more

“Very important” is an effective synonym you can use. It shows that someone is “important” to a team, meaning they’ve helped people out in more than just one way. Also, “… See more

“Very useful” is another great choice. “Very” is used as an adverb again to show that someone goes above and beyond in achieving the things they do. If someone is “useful” to … See more