According to the western media the Wagner Group as the very worst of the worst. They are officially a transnational criminal organization, that is made up primarily of convicted felons, and a 'grizzly cult', that uses human wave attacks because it has no respect for life.

“A lot of the content that I see on Telegram and elsewhere is eerily reminiscent of neo-Nazi propaganda, which is an aesthetic that they seem to have copied,” said Colin P. Clarke, the director of policy and research at the Soufan Group, a global intelligence and security consulting firm that monitors Wagner activity online. “It makes sense given the audience they are trying to recruit, who are, essentially, for lack of a better word, sociopaths.”

I don't know what is true about the Wagner Group. They could be cannibals and Satan-worshippers for all I know.
Ukrainian's mercenaries by contrast, are humble, patriotic warriors fighting for democracy.

Volodymyr Zelensky reassured his compatriots yesterday: “Ukraine is already welcoming foreign volunteers who are coming to our country. First ones from 16,000. They are coming to defend freedom, defend life. For us, for everyone. And it will be a success, I’m sure.”

Who who are these people fighting for freedom and life? The first word that comes to mind is - Blackwater.

“We also have information on US instructors of private military companies taking part in the training process, such as Forward Observations Group and Academi,” he said.
The National Corps party was formerly known as the Patriots of Ukraine. Its core base of support comes from the neonazi Azov battalion, which has since been integrated into the Ukrainian army.

Tucker brings on Erik Prince, who claims he pitched a plan to the Administration in Dec to have 140 fighter planes that were about to be retired from service sent to Ukraine, flown by mercenary pilots, and that Putin wouldn’t have invaded if Biden had agreed to his plan. pic.twitter.com/vz7c8vBLwk

— Ron Filipkowski (@RonFilipkowski) February 25, 2022

However, Blackwater (aka Academi), and it's less than spotless reputation, is old news. They've been upstaged by the new kid on the block - Mozart Group.
Mozart was founded just weeks after the war started in 2022, by former officers in the U.S. Marines Andy Milburn, a high-profile supporter of the Ukraine and and Andrew Bain, a businessman who has lived in Ukraine for over 30 years. One New York Times article said that, for Milburn, “Ukraine represents the morally just war that eluded him his entire career.”

By April 2022, Mozart quickly became a media favorite given its emphasis on conducting primarily humanitarian assistance and military training.

The Mozart Group collapsed a few weeks ago. It existed for less than a year. What happened?

The core problem is that TMG was structured as a limited liability company registered in Wyoming. But Milburn and TMG had encouraged tax-exempt donations through its “alter ego” humanitarian organization, Task Force Sunflower [TFS].

The key difference between LLCs and nonprofits is what they do with the money they generate: LLCs can choose to distribute profits from their business operations, products, and services to their owners. Nonprofits must use revenue after operating expenses and employee salaries to carry out their mission. Nonprofits do not have to pay federal taxes, whereas LLCs do.

Then on January 10, Bain sued Milburn.

filed a lawsuit against Mozart's leader Milburn in Wyoming state, where the group is registered, on charges of "financial fraud, sexual misconduct, burglary, attempted bribery, avoidance of U.S. weapons-transfer regulations, and even threatening a retired American general."
Bain, who says he owns the majority of shares in the military group, said that the head of Mozart Milburn managed the group “in a manner which has caused senior Ukrainian military officers to remark ‘can’t he go home and stop saving our country.’”

Milburn struck back by accusing Bain of trying to sell Mozart group to the Taliban.