Well it is reporting the latest version, so it is possible it had completed before it stalled. In which case no need to reinstall, just monitor your use of avast for any anomalies/issues.

Sorry but a clean reinstall is more likely to resolve a problem with the avast installation than end up requiring a reformat and Operating System reinstall.

There are a great many people were we recommended a clean reinstall and the likelihood of subsequently requiring a reformat, represent a very small fraction of a percent of those doing a clean reinstall.