A vicious villain am I
Absolutely heinous indeed
The greatest of my kind
There's nothing worse
Covering the face of the Earth
The planet is literally infested with people who can't spell.
A fiend of all mankind
Even intelligent people are sometimes affected.
Although I may appear weak and small
Many people think it doesn't matter...
Great power I am assigned
...but those people are wrong, it does matter. People don't get jobs, they get ridiculed, they miss out on business opportunities, they are ignored, etc. all because they spell something wrong and are branded an idiot by the reader, who subsequently treats the entire message with disdain.
Those who fail to heed my warning
Some people don't even notice them...
Condemnation they will find
Oh yes - they will be condemned all right!
Two natures do I have
Well there's the one where people simply don't realise that "their" and "there", and "your" and "you're" are actually different words, then there's the one where they just spell something wrong, for example "definately". There's also the kind where British people use "realise" as I did above, and American people use "realize", but technically these are alternate spellings rather than errors, although they may be used by mistake. There's also the one where people accidentally type a different word than they meant to, like "thought" instead of "though", but that's a typing error, or 'typo'. So that's just two natures, since the last two don't count.
A son of God and of the Devil
Jesus couldn't spell for toffee, and the devil's in the details!
Though temples have been built to me
We have plenty of temples to educate against spelling errors, and to mock them: web pages; info-graphics; books; comedy sketches; YouTube videos; etc. (oh, and schools, but I'm not sure they do as good a job as any of the others).
Thieves are exalted to a higher level
That's because it's spelt correctly, it's not "Thiefs".
A loud cry sounds from the town
Every time someone has to suffer the eye-stabbing pain that results from spelling errors.
Gloriously is my appearance made
We revel in pointing them out.
Considered me not your enemy
That's true - it's not your fault, it's the guy writing it.
And you will have nothing of which to be afraid
Those who embrace spelling errors by simply not knowing or caring have nothing to fear. They are oblivious to the horrible path of destruction they leave in their wake.
Answer this puzzle and you will see
All my secrets be made clear
Please tell me this means if I get this puzzle right I'll never have to suffer spelling errors again, and I'll never make any myself and have that awful feeling of disgust for myself when I realise my error.
Consider, though, as you proceede
Ahh, a sneaky clue... I see what you did there!
All riddles are not as they appear
That's right, this entire riddle was just to point out that single spelling error on the previous line... devious... very devious indeed my friend!
Now if that's not lateral thinking, I don't know what is :P