git branch -D ((git branch | Select-String -Pattern '^\s*3\.2\..*') | foreach{$_.ToString().Trim()})
//this will remove all branches starting with 3.2.
git branch -D ((git branch | Select-String -Pattern 'feature-*') | foreach{$_.ToString().Trim()})
// this will delete all branches that contains the word "feature-" as a substring.
git branch | grep "<pattern>" (preview of the branches based on pattern)
git branch | grep "<pattern>" | xargs git branch -D (replace the <pattern> with a regular expression to match your branch names)