Unexpected plots for active low pass filter response in LTspice
In the first circuit the active Low Pass filter is a 2nd order filter while the passive Low Pass filter is a 1st order filter so I totally expect the curves to be different and they are what they should be.

In the second circuit you're expecting the impossible from that poor LM324 opamp. You give it a single (positive only) supply yet the circuit expects it to be able to output negative voltages as well. That's not going to happen unless you supply the LM324 with a symmetric power supply so for example +5 V and - 5 V.

In your circuit the LM324 cannot amplify properly and that's what we see in the plot as well.

So connect the negative supply rail of the LM324 not to ground but to a -12 V (for example) supply. You have to add another voltage source for that!