His biggest failure?
In my opinion conflict he caused in Ukraine, and all bad results Russia received from it, including trade lost with EU.
Because of Putin all former Easter block (Poland, Ukraine etc) demanding that Nato soldiers came in their countries and protect them from Russia.
It's big strategic mistake because Russia lost their influence in this area.
He actually achieved a great victory there, he occupied Crimea, and shifted the focus towards Syria by supporting the rebels, provoking Turkey, USA etc.
When is the last time your heard something about Ukraine on the news?
Putin is a smart guy, everyone's worried about ISIS, some ships and airplanes in the middle east, completely forgetting the invasion
Eastern block asking for NATO soldiers? (Ukraine is Russia, btw)
Since when is that?