Why does fiction often portray an albino as the bad guy?
Off the top of my head I can list off several:
Tombstone of Marvel Comics
https://images.search.yahoo.com/yhs/search;_ylt=A0LEVjesA3JZPTQAQf4nnIlQ?p=marvel+tombstone&fr=yhs-mozilla-002&fr2=piv-web&hspart=mozilla&hsimp=yhs-002
Dar Robinson’s “Moke” in Stick
I gotta agree, that is seriously beyond the pale.
There was an albino assassin in The Da Vinci Code.
Somebody made a list: Home | Skinema (Note: this is a list of all albino characters but you can see they’re mostly portrayed as evil.)
I see what you did there. 
We must work to turn albino into an albiyes!
Well there was the good albino looking guy in Powder who also appears to have Alopecia.
I’ve no idea how they were treated in real life in the West, partially because I’ve never met one, but I understand that some have been ill-treated in the African continent and they don’t live long there. China too has had superstitions about them.
Was this Bond villain meant to be an albino?
Relevant TV Trope.
Counter relevant TV Trope.
As to OP, why evil? I dunno. Red eyes, maybe? But there are plenty of albino heroes in fiction that there probably isn’t any fixed reason, other than superstition. Which persists IRL today in some parts of the world.
He was a genetically engineered steroid-enhanced Nazi, but not an albino.
I forget, was Gary Busey’s character in Lethal Weapon an albino?
But it isn’t because they are thought to be bad people–they are considered to make good medicine.
Do they die of pinkeye?
“Whitey” Jackson (William Frankfather) in the 1978 Chevy Chase movie Foul Play
Not having read any of the TVtropes articles or anything my guess would be it’s because they’re angry over their upbringing.
Ironically enough, I’m reading a book right now (The Seventh Plague by James Rollins) which features Albino twins as enemies. They’re assassins/killers and such because they were abused and ridiculed for their looks that they wanted revenge and became bad.
It’s an easy story to tell “person who is different is angry at their oppressors” so I doubt it’s a bias or prejudice and more laziness of storytelling
The Albino Nazi in The Eiger Sanction.
There was an albino villain in “Banshee”. He was called, wait for it, the albino.
“Where did we leave that albino’s wheelbarrow?”
“With the albino, I think.”
Those not murdered for bodyparts tend to die in their mid-40’s of skin cancer, for a serious answer to a maybe not so serious question.
