I want to present the facts and nothing but the facts.

Let's start with the railway workers dispute, by far the biggest slam against the Biden Administration.
The biggest grievance was the horrible railroad attendance policy.

In the system, each worker starts with 30 points and loses points for taking a day off. Workers can accrue 4 points by being on-call for 14 straight days, but any time off, even for illness or a family emergency, resets the clock

Most rail workers didn't get any sick days.
The agreement got rid of the worst parts of the contract.

Workers also can take time off for routine doctor’s appointments without being penalized, and would not lose attendance points for hospitalizations and surgical procedures, according to the Brotherhood of Locomotive Engineers and Trainmen.

Something that got overlooked was that the Biden Administration has kept up the pressure on the railroads.

One of the largest freight railroads in the world, CSX, announced a deal with two rail unions, including Weaver's, to provide four days of paid sick leave annually, plus the option of converting three personal days into additional paid sick time.

It's actually very unusual that the Biden Admin has not broadcast this success, eventhough the IBEW gave them credit as most of the other rail unions got the same deal. So now they have seven sick days.
In contrast, Republicans in Congress voted against rail workers having ANY paid sick days.

Now the NLRB:

Indeed, on his very first day in office, Biden, at the urging of labor advocates, removed then-General Counsel of the NLRB Peter Robb, a deeply anti-labor attorney appointed by Trump, from his post...
To replace the ousted Peter Robb, Biden installed former labor lawyer Jennifer Abruzzo, who, strongly endorsed by unions, has been remarkably effective and successful, rapidly emerging as the most pro-union GC in decades. Abruzzo has released a series of memos advising the Board to, among other things, ban captive audience meetings, expand the coverage of federal labor protections, strengthen the Board’s enforcement powers and remedial arsenal, and facilitate the union organizing process, policies which she has urged the Board to adopt in countless cases her office has prosecuted before the agency. For its part, the Board’s Democratic majority—including two Biden appointees—has proven largely receptive to the GC’s progressive proposals. The agency’s recent Cemex decision, for example, is one of several rulings and regulations the Biden Board has promulgated to facilitate organizing and collective bargaining, and its potential to meaningfully deter unlawful employer obstruction of organizing drives has excited labor proponents. Moreover, since Biden’s inauguration, the NLRB has intensified its processing of ULP charges and election petitions—and unions have prevailed in a higher percentage of such proceedings.

The NLRB has ordered corporations to reinstate more illegally fired workers in the first year of the Biden administration than it did during all four years of the Trump administration. The Biden administration updated Davis-Bacon standards to prevent federal construction contractors from paying below-market wages.
Biden's NLRB had made it easier for workers to organize as well.

On Aug. 24, the NLRB issued a final rule that will speed up union elections, screwing up Step 2 of employers’ union-busting playbook. The rule, effective Dec. 26, will eliminate common delay tactics that help employers: pointless waiting periods, the chance to request numerous extensions, and the opportunity to flood the process with irrelevant arguments.

According to the Economic Policy Institute, petitions for union elections grew by 53 percent between October 2021 and September 2022. Moreover, the rate at which workers win unions in NLRB elections climbed steadily during the first two years of the Biden administration, exceeding any level achieved under the previous administration.
In 2024, the Biden administration has picked up the pace.

In the month of April alone, it banned the noncompete clauses that can stop workers from taking another job in their same line of work if they quit, expanded eligibility for overtime pay to people making up to US$58,656 a year, up from its current cap of $35,568, and pushed pension funds to only invest in companies that adhere to high labor standards.

I recognize that not everyone considers this to be an important issue, but for me the status of labor unions is the weather-vane of the working class.