Lately, I've watched a series of interviews with Yvegeny Prigozhin, the head of the Wagner Group. Unfortunately, the videos are in Russian (naturally) and not subtitled in English.
He's an interesting character. After serving a brief prison term as a young man, he started a number of businesses including grocery supplies, catering, restaurants, casinos and, eventually, the Wagner Group.
Despite very close ties with Putin, Prigozhin has been an outspoken critic of Putin, the GRU (Russian military intelligence) and the Russian military in Ukraine. The Wagner Group has played a prominent role in Ukraine, Syria and Central Africa. It has also been accused of war crimes in Ukraine and elsewhere.
Some in Russia see him as Putin's successor.