Rome again, Rome again, giggity gig

I used to think Caligula was the worst Roman emperor and Nero second worst, but I am beginning to change my mind.  No longer so sure.

I was familiar with the antic of Little Boots and Nero, and familiarity breeds contempt.  The ones I, personally, was unfamiliar with are as bad or worse.

Tiberius, before Nero, had a lot of bad press after death.  He'd diddle little boys and kick em off a cliff into the sea when he was done with them.  But he was probably only a child rapist, not child murderer.  The histories were unkind to all the bad emperors and probaby exagerrated the negatives quite a bit.  But even if you discount a lot of the reports these are all bad.
Commodus.  Joaquin Phoenix.  Concentrated on being a gladiator and thusly ran the empire into the ground.  You know how Phoenix played him in the movie?  He actually toned it DOWN from the reality. 
Caracalla? Awful
Elagabus? Also.

They were all either:

Murderous, delusional, tryannical, perverts, or,
Murderous, psychopathic, tryannical, perverts, or,
Murderous, sociopathic, tryannical, perverts, or,
In one case, a murderous, paranoid, tryannical, pervert.

And by 'pervert', I don't mean sexual deviants your great grandma would be horrified by, or YOU would disapprove of, but perverts by their own contemporary Roman standards.  And, in many ways, Rome was much more loosey goosey the the more libertine 5% of modern society.

The usual common motif is a early 20's or younger boy was given absolute power and had noother authority that could temper his impulses.  And that power corrupted him.

So, how to you measure the WORST emperor?  Body count by genocide?  Caracalla?  Reigned the longest so had the longest time to sap an empires resources?  Commodus?  Craziest?  Caligula.

And I am only up to the mid 3rd Century.