"mtk-su failed critical init step 3" typically occurs when the MediaTek rooting script lacks the necessary execution permissions or the device's security patches have blocked the exploit Best Fixes to Resolve the Error Re-issue Execution Permissions
If the software-based exploit fails at Step 3, the device's security may be preventing the "handshake."
The Fix: Manually supply the --offset parameter.
"I want to fix Step 3 so no one else ever has to."