It's a long list. In the interest of not getting Carpal Tunnel Syndrome, I will limit this to only 8:
1) Trump and his aides softened the GOP platform on Russia's annexation of the Crimean Peninsula in the Ukraine. Ahead of the 2016 Republican National Convention, Trump campaign aides blocked language from the party platform that called for the US government to send lethal weapons to Ukraine for its war against Russian proxies. While the Trump Administration ultimately did supply arms and anti-tank weapons to the Ukraine, this was a hollow gesture, because the Ukrainians can't use the Javelin missiles in the conflict against pro-Russian separatists based on the terms of the sale. A top staffer in the US embassy in Ukraine testified last November that the Javelins aren't "actively employed in combat operations right now."
2) Trump has repeatedly lobbied for Russia to be readmitted to the G 7, even after he learned of the intelligence reports of Russian bounties being paid to the Taliban to kill American soldiers.
3) Trump proposed a cyber unit with Russia. After the July 2017 meeting of G 20 leaders, Trump said he had spoken with Putin about "forming an impenetrable Cyber Security unit" to combat "election hacking." Trump quickly backtracked after Congressional leaders from both parties said it would be ridiculous to work with Russia on cybersecurity because Russia was responsible for egregious hacks against American targets, including during the 2016 Presidential election.
4) During the Helsinki Summit in July of 2018, President Trump memorably sided with Vladimir Putin's denial of Russian involvement in the hacking of the DNC, against the conclusion of his own appointed Director of National Intelligence, Dan Coats. Trump later claimed that he had misspoken... but since Trump has once again sided with Putin's denial following the Helsinki Summit, that appears to have been another Trump lie.
5) Trump eased sanctions on Russian oligarch, Oleg Deripaska, along with the three companies linked to him. The US Treasury Department sanctioned Deripaska in 2016 over his support for Russian interference in the 2016 election. In a bipartisan rebuke of the removal of these sanctions, 11 Senate Republicans supported a Democratic resolution calling for these sanctions to remain. Trump was undeterred, and still removed the sanctions, anyway.
6) Trump's withdrawal from Syria gave Vladimir Putin a key boost. Trump announced in October of 2019 that US troops were withdrawing from northern Syria. This abrupt move cleared the way for Turkey to conquer territories previously controlled by the US and allied Kurdish militias. It also gave Russia a golden opportunity to expand its influence and swiftly take over abandoned US outposts and checkpoints. This has been crucial for Putin's agenda in the region.
7) Trump repeated Kremlin talking points on ISIS. After announcing the Syrian withdrawal, Trump repeated the Kremlin talking point that, "Russia hates ISIS as much as the United States does," and that they are equal partners in the fight. However, Trump's comments don't reflect the reality on the ground. Since intervening in Syria in 2015, the Russian military has focused its airstrikes on anti-government rebels, not ISIS.
8) Trump just ordered US troops out of Germany. The plan to remove about one-third of the force drew serious concerns from the Pentagon because it could compromise Europe-based defenses against Russia. In a letter to Trump, nearly two dozen Republican lawmakers said his decision would "strengthen the position of Russia to our detriment." However, that seems to be Donald Trump's across-the-board, foreign policy objective. "Make Russia Great Again!"
