There's no such thing as video compressor because almost all of common video formats are already highly compressed codecs like H264 that is used mostly in MP4 and MKVs.

The only way you can shrink a video file is by actually decreasing its quality or removing some extra tracks like audio in other languages if it had in it.

You can lower resolution to 720p but first I recommend you to install MediaInfo software to see actual Bitrate of your video with it, then you can divide it by 2 in a calculator then use it as constant Bitrate in any encoder software.

I say divide Bitrate by 2 because you're going to get half of resolution (720p instead of 1080p) then you'll need only half of video Bitrate too. This way you can shrink file in a good amount of size.

Just be careful about KBs or MBs in Bitrate, if Bitrate is in MB but your encoder software only accept KB then you need to convert MB to KB before doing divide thing.

As encoder software, I recommend Avidemux or Handbrake but if you want something more easy to use you can use Format Factory too but beware it's have bundles in its installation that you have be careful to doesn't agree to install.