Microsoft Defender is found to be one of the worst performers in AV-Comparatives test suite which measured performance impact by anti-malware apps. AV-TEST also found similar results.
After very poor showings in terms of system performance impact in AV-TEST's and AV-Comparatives' reports, Microsoft Defender does really well in the latter's malware protection ranking.
AV-Comparatives recently released its Performance test for the month of October 2022. In the evaluation, Microsoft Defender was found to be the worst offender with the highest performance impact.