user5463: 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? 

user-1: 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 & for entering into right view: This is one's right effort. One is mindful to abandon wrong view & to enter & remain in right view: This is one's right mindfulness. Thus these three qualities — right view, right effort, & right mindfulness — run & circle around right view.

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

user11009: Buddha means the person who has already eradicated attachment, aversion and ignorance. Hence there is no evil Buddha's. The Buddhist term for them is the "Mara" the opposite of Buddha. 
The people who practice mindfulness and concentration without the backing of Noble Eightfold Path is called "wrong mindfulness" or "Mitya Sati and Mitya Samadhi"

5463: <p>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? </p>
 -1: <p>This is highly anecdotal, but... Behring Breivik allegedly had a great interest in mindfulness meditation.</p>

<p><a href="https://www.theguardian.com/commentisfree/belief/2012/may/22/anders-behring-breivik-meditation" rel="nofollow noreferrer">https://www.theguardian.com/commentisfree/belief/2012/may/22/anders-behring-breivik-meditation</a></p>

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

<blockquote>
  <p>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.</p>
</blockquote>

<p><a href="https://www.accesstoinsight.org/tipitaka/mn/mn.117.than.html" rel="nofollow noreferrer">https://www.accesstoinsight.org/tipitaka/mn/mn.117.than.html</a></p>
 11009: <p>Buddha means the person who has already eradicated attachment, aversion and ignorance. Hence there is no evil Buddha's. The Buddhist term for them is the "Mara" the opposite of Buddha. 
The people who practice mindfulness and concentration without the backing of Noble Eightfold Path is called "wrong mindfulness" or "Mitya Sati and Mitya Samadhi"</p>
