Cases of psychopathy According to this Learning-Mind website, the 3 basic behaviors of a person  which indicate likely psychopathy are 


Unhealthy obsession around arson
Cruelty to animals 
Bed wetting after the age of five years old


This has been described as the MacDonald triad. 

So if 2 out of the 3 behaviors are found in one person, does that mean that he/she is certainly a psychopath? How predictive is the MacDonald triad?

How treatable is psychopathy? How can one if they have three of the MacDonald triad and have been diagnosed with psychopathy to not to behave like that?

This 2012 question discussed the definition of psychopathy - Are there any standard tests to measure psychopathy?

And so does this 2009 question - What is the proper definition of psychopathy?
Psychopathy and the MacDonald triad

Just keep in mind that psychopathy is often used as a more popular term for the characteristics of Anti-Social Personality Disorder (Davey, 2014). The three behaviors described by the website were indeed studied in the scientific community (see MacDonald). First of all, this research was retrospective and descriptive which in no way provides a causal link between the three factors and psychopathy. In other words, those three factors (or even two of them) are by no means the cause of psychopathy. In order to establish a true causal link between those three factors and psychopathy an experiment would be necessary (Passer, 2019) which is virtually impossible in this case.

Subsequent research has also criticized the validity of the MacDonald triad, suggesting that it likely has low predictive power for Psychopathy (Parfitt &amp; Alleyne, 2018; Ryan, 2009). People who show all three factors of the MacDonald triad may very well not be psychopaths.

Treatment of psychopathy

As for treatment of psychopathy, clinicians have experienced that treatment of psychopathy is very difficult if not impossible. When psychopaths are caught after a crime they often have to participate in rehabilitation programs but these are general ineffective (Butcher, Mineka &amp; Hooley, 2017). Some studies show that treatments which are effective for other criminal offenders actually lead to higher reoffending in psychopaths (Harris &amp; Rice, 2006). Especially treatment focused on social skills and empathy seem to have counterproductive results because it makes the psychopath even more charming and socially cunning (Vitale &amp; Newman, 2008).

Biological treatments such as drug therapies have not been systematically studied but so far show modest changes at best, leading scientist wondering whether these are worth studying more systematically. Overall these biological treatments seem to have little impact on the indivudal with psychopathy. Also, even if these treatments could help, psychopaths are still likely to be unmotivated to take medicines for example (Butcher et al., 2017).

Lastly, cognitive behavioral therapies seem to be most promising. These therapies often focus on a few specific factors, as can be read in Butcher et al. (2014):


  Common targets of cognitive-behavioral interventions include the following: (1) increasing self-control, self-critical thinking, and social perspective taking; (2) increasing victim awareness; (3) teaching anger management; (4) changing antisocial attitudes; and (5) curing drug addiction.


However, even CBT is relatively (to other disorders) not very effective for psychopathy, as Butcher et al. (2017) write:


  Even the best of these multifaceted, cognitive- behaviorally oriented treatment programs generally produce only modest changes, although they are somewhat more effective in treating young offenders (teenagers) than older offenders, who are often hard-core, lifelong psychopaths


For further reading about treatment see chapter 10 of Butcher et al. about personality disorders.

I personally believe psychopathy is one of the more serious disorders (do not get me wrong, all disorders negatively affect people), mainly because hatred and incomprehension for these individuals is very high even though in most cases there is hardly anything they can do about it.

References

Butcher, J. N., Mineka, S., &amp; Hooley, J. M. (2017). Abnormal psychology (17th ed.). Boston: Pearson.

Davey G. (2014). Psychopathology: Research, Assessment &amp; Treatment in Clinical Psychology (2nd ed). British Psychological Association and John Wiley &amp; Sons LTD.

Harris, G. T., &amp; Rice, M. E. (2006). Treatment of psychopathy: A review of empirical findings. In C. J. Patrick (Ed.), Handbook of the psychopathy (pp. 555–72). New York: Guilford Press.

Parfitt, C., &amp; Alleyne, E. (2018). Not the sum of its parts: A critical review of the macdonald triad. Trauma, Violence, &amp; Abuse, (2018). doi:10.1177/1524838018764164

Passer, M. (2019). RESEARCH METHODS: Concepts and connections. S.l.: WORTH PUB.

Ryan, K. (2009). The Macdonald triad: Predictor of violence or urban myth?.

Vitale, J. E., &amp; Newman, J. P. (2008). Psychopathy
as psychopathology: Key developments in etiology, assessment, and treatment. In W. E. Craighead, D. J. Miklowitz, &amp; L. W. Craighead (Eds.), Psychopathology: History, diagnosis, and empirical foundations (pp. 565–97). Hoboken, NJ: John Wiley &amp; Sons.