Most presidents seem to end up pardoning some unsavory characters. It's been happening since at least Reagan.
It's not my job to comment on every single political development or every presidential pardon, and I've detailed what exactly about the mass pardon of the 300 or so people convicted of attacking the police in Trump's name is different. But, ok. I'll try and respond.
Biden did not pardon Leanard Peltier, who I assume is the cop killer in question since you provided no names. I don't support that commutation (no pardon and confined to his home until he dies, which is likely soon), but he had quite a number of people and organizations who did.
James H. Reynolds, the US Attorney who prosecuted the case, has publicly apologized for irregularities in the prosecution and has called for his pardon.
In December, 33 US lawmakers sent a letter to Biden calling for Peltier's clemency due to irregularities with his prosecution.
The Pope and a number of Human Rights organizations have done the same, for the same reasons.
Who are the equivalent lawmakers or organizations requesting clemency for the 300 or so people convicted of violent felonies against the police? Most of the GOP comments I've seen on the most egregious pardons have been critical of Trump's move, for obvious reasons.
Biden communed a number of former death sentences to life in prison, so I am assuming that group includes the child rapists and murderers you are referencing. That is in no way the same and letting them walk free.
If you have some specific names, I'd be glad to comment on them.
