Bookmark the official VLC for Android download page and ignore every other "codec pack" website. Your phone (and your data) will thank you.
VLC for Android provides several built-in tools to enhance the playback of Xvid-encoded content: Universal Format Support xvid video codec vlc android apk download
Once VLC is installed, here is how to get your Xvid (.avi) files playing. Bookmark the official VLC for Android download page
Most Android smartphones do not natively support Xvid playback. Why? xvid video codec vlc android apk download