I’ve put together a timeline of Flynn and Russia. It’s almost certainly incomplete. It’s just what I have been able put together as a non-reporter with mediocre research skills, from what’s been reported in the press. And it definitely appears to be damning for everyone connected with him:
August 7, 2014: Michael Flynn is fired for his "chaotic" management style and also for installing a secret internet connection in his Pentagon office.
October 8, 2014: The DIA advises Flynn that he must receive advance approval to receive any payment from a foreign government or an entity that may be controlled by a foreign government.
December 10, 2015: Flynn is paid to speak at a gala put on by Russian propaganda outlet RT, and is placed next to Putin. He does not receive prior approval or report this payment.
February 2016: Flynn begins advising the Trump campaign.
September 19, 2016: Flynn is hired by a Russian-connected Turkish lobbying group.
November 10, 2016: President Obama warns Trump against hiring Flynn. The Obama administration repeatedly informs the Trump transition team that things are not on the up and up with Flynn.
November 18, 2016: Trump names Flynn as his National Security Adviser, and begins sending Flynn to receive intelligence briefings on his behalf.
Late November, 2016: Flynn subordinate Michael Billingslea requests Russian ambassador/intelligence operative's classified CIA bio.
December 29, 2016: New sanctions announced on Russia in retaliation for hacking related to the election. Flynn immediately speaks on the phone with Russian ambassador/intelligence operative Sergey Kislyak.
January 15, 2017: News of the Kislyak call leaks. Pence appears on Face the Nation to deny that the conversation involved sanctions.
January 19, 2017: Obama administration discusses what to do about Flynn. FBI Director James Comey opposes notifying Trump Administration because it could impede the investigation.
January 20, 2017: Despite the repeated warnings, Flynn is sworn in as National Security Adviser.
January 22, 2017: The Wall Street Journal breaks the news that Flynn's Russian connections are the subject of a counterintelligence investigation.
January 24, 2017: Flynn is interviewed by the FBI about Russia.
January 26, 2017: Acting Attorney General Sally Yates warns White House counsel Don McGahn that Flynn's failure to disclose his Russian connections makes him vulnerable to blackmail.
January 27, 2017: McGahn calls Yates back to the White House, demands to know “Why does it matter to the Department of Justice whether one White House official lies to another White House official?”
January 30, 2017: Yates receives a note from the White House notifying her that she has been fired.
February 9, 2017: Washington Post reports Flynn discussed sanctions on the December 29 call with Kislyak alongside Flynn’s denial.
February 13, 2017: Washington Post reports on the Yates warning. Flynn resigns.
March 7, 2017: Flynn finally registers as a foreign agent for the job he's had for the past six months.
So...that’s what happened. I’m sure I missed a few things, but what I know seems damning of the entire administration, and what I don’t know could fill encyclopediae.