MX player is a very renowned player in android which is very popular for it’s codecs and high efficiency for video playing even in low end phones. I personally have been using it for years now and without doubt can say by far the best player.
Many people say that it’s a bit buggy, which is, so I would suggest them to try their nighly versions which are a tad bit more stable when video streaming is considered.
All in all, this player is a boom. Would easily play Full hd videos or even 2k in a 720p reso phones. Their codecs are highly efficient.