1) On day one in office, President Biden stops some agreements we had with Mexico regarding keeping people on their side of the border. Kamala Harris basically tweeted: "Come one, come all, no more wall!" The President of Nicaragua made the statement that her tweet was ill informed. They immediately began re-training border patrol agents for a catch and release program. It only took about a week, for illegal immigrants to flood our border and it continues with horrendous consequences especially for women and children.
2) Right off the bat, he discontinued arrangements with Israel and let various Arab nations know this in hopes of gaining favor; basically throwing Israel under the bus. The Trump Administration helped broker a deal for peace and next thing we know, it's Jews versus Muslims again. Obama did the same thing with Israel. He flew right past the country, one of our greatest allies even in U.N. votes (they've got our back, the Arab nations don't), and began meeting with leaders from other middle-eastern countries. Everything is a mess now and in need of serious policy moves.
3) Democrats and Republicans, led by Ted Cruz, put together sanctions to stop Russia from building the natural gas pipeline to Germany. They worked, both parties did a great job as Russia backed down for over a year. And now the Biden Administration, confusing even democrats who worked on the sanctions, lifts them from Russia and they began building the pipeline again five days after he was in office. I hope the question of "why," he did it is answered because I can't make any sense out of it. Democrats and the mainstream media, said Trump was tied to Russia yet his entire time in office was spent taking away their power including in the middle-east where they were trying to get a foothold starting with Syria. Now we know who's truly tied to China and Russia and we had better figure out why before it's too late. Putin is a terrorists. We had him with taking away the pipeline and hurting their economy tremendously, but Biden let him slip away. Now they can build their military strength because they will be open for business in Germany and then Germany will make money by distributing the natural gas to other nations.
There are many more, but I've given you the top three which are on my mind right now. Biden has been a godsend for Obama's legacy because Obama's no longer the worst president we've ever had.