Evil Buddha, anyone? If a person practices mindfulness and concentration with great success but doesn't care about Noble Eightfold Path, is there a possibility of creating so to say "Evil (or at least immoral) Buddha"?
Were there any historical examples of such people?
This is highly anecdotal, but... Behring Breivik allegedly had a great interest in mindfulness meditation.

https://www.theguardian.com/commentisfree/belief/2012/may/22/anders-behring-breivik-meditation

It is no coincidence that Sila is such a central aspect of buddhism. You can't reach buddhahood without it:


  One makes an effort for the abandoning of wrong view &amp; for entering into right view: This is one's right effort. One is mindful to abandon wrong view &amp; to enter &amp; remain in right view: This is one's right mindfulness. Thus these three qualities — right view, right effort, &amp; right mindfulness — run &amp; circle around right view.


https://www.accesstoinsight.org/tipitaka/mn/mn.117.than.html