A) Mueller Report
As a private citizen, Barr attacked the Special Counsel investigation per his 19 page memo in June 2018, which most folks describe as Barr's "job application" for the AG job. During his confirmation hearings, Barr, under oath, testified he would be above reproach. he wasn.t
After the Mueller Report was sent to DOJ, Barr manipulated the release of the report (sat on for 4 weeks), misrepresenting and mischaracterizing its findings in his March 24th, 2019 letter to Congress, clearly to benefit Trump.
B) Follow up prosecutions
When the Special Counsel closed shop, all remaining work was handed over to the US Attorney in DC -- Jessie Liu -- a Republican Trump appointee, but well regarded within the DOJ. Recently, Liu was ousted and replaced with Tim Shea -- a close and loyal aide to Barr. The very next day, the DOJ changed their sentencing recommendation re Michael Flynn from 6 months prison to probation. One week later, the DOJ changed their sentencing recommendation re Stone from bottom of the guidelines to a "substantial reduction" consistent with Trump's tweets. The 4 prosecutors who tried the case immediately resigned.
The DOJ is also now set to close down investigations from that office (US Atty DC) re Erik Prince and Rudy.
C) Ukraine
Barr is mentioned 5x by name in the 7/25 call between Trump and President Zelensky. Barr should have recused himself. He did not even consult w/ DOJ Ethics Office (why they exist). Instead, even though the Whisteblower statute demands that WB complaint goes to Congress, Barr attempted to thwart the complaint from going to Congress per a DOJ memo saying Congress does not have to get the WB complaints. Total horseshit.
Even though Rudy remains a target re SDNY investigation re Ukraine, Barr has established a special intake process for Rudy to brief DOJ on the info he gathered re Ukraine (as if Rudy was not acting at the behest of Trump in the first place).
D) 2016 Russia investigation
Even though DOJ IG Horowitz found FBI errors re FISA warrants re Carter Page, the seasoned DEPARTMENT OF JUSTICE Inspector General determined that DOJ/FBI had a sufficient basis to launch the investigation in 2016, and concluded that the DOJ/FBI officials acted without political bias.
Barr publicly attacked his own Inspector General's report while appointing Durham to run with a criminal investigation, -- that is to outflank the IG of his own department -- again, to politically benefit Trump and discredit the 2016 Russian investigation (the same one that Mueller found that Trump had obstructed justice)
***********
If you want to live in a country that investigates and prosecutes anyone who is either a political rival of the President, or a federal agent who has the audacity to investigate potential treason/collusion, then Trump and Barr are your men.
If you want to live in a country that undermines and obstructs active investigations or prosecutions of the President's allies and friends, then Trump and Barr are your men.