How I see it... for those who might care.
SPOILERS
Sorry, I won't manage to get constructive here, so I'll post as a train-of-thought if you don't mind. Read it as my own thoughts, which are a mix of film lines and what I take of them:
Who are you?
Amnesia
Cure
Who are you? A detective? A policeman? A nurse? A beast with his killing instincts suppressed by moral and social codes.
What drives a murderer to kill? Sometimes it's hard to tell. Or so simple one might overlook it.
Hanged wife. Feeling of despair. But is it really? Or just his mind actually wishing for it?
The policemen shot his colleague because he hated him. What was the reason? Didn't he just told it? He hated him. Why go so far as killing? His mind is empty. No codes. Cure.
Empty. Empty Mind. Amnesia. Who are you?
Who am I? I want to know about you.
I hate men for looking down on me.
I hate my wife for (something related with a pink negligee. Betrayal?)
I hate my wife for being a burden.
Did you tell him about me/my wife? ... Well he keeps asking questions (The guard probably told mamiya nothing about the detective's wife. He just knows all this stuff about everyone. Everything people hold within, which consumes them from the inside)
Deep down in our minds we often wish for the worst, even in those close to us. There's a barrier protecting us from going further, but what if that barrier was removed?
What's with the monkey? It has a cross on his neck. It also seems like he was burned up. What's with the live monkey? He always shows up followed by a furnace. Mamiya got burned burning the monkey before making the cross on his neck? Possible. Maybe he just hates monkeys? Or animals in general? There were a lot in cages. And he lived surrounded by them until 6 months ago.
The girl in the last scene. She grabs a knife after a girl calls for her. She's going to kill her boss? Possible. Hypnotized? Why hypnotized? Maybe just usual human stuff. Reasons? Unimportant. She hates her job, she hates her boss? No need to be hypnotized to kill. People kill for any reason. Some just hold their grudges within while others can't cope with it. The waitress his going to kill and she's not hypnotized. She's just being "pure", as in human without constraints.
Our hate has no boundaries. That's who we are. We would consume everything around us if we could. Why can't we? What holds us back?
"Lunatics have it easy in this world while the rest have to struggle through it."
Mamiya gave those people what they really wished for, deep down in their true selves. He gave them a cure.
A guy surrounded by animals that hates animals.
A women surrounded by men that hates men.
A teacher and a lawyer who hate their wife.
A Psychiatrist living alone that hates himself.
An old women who hates her son.
Our love has no comparation to our hate and the first is only a farce, a mask we show off, who hides our true selves and our most defining characteristic. Hate.
Blank Face in poster. Nurse removing skin from the man's face. What we show outside is a farce. It's blank non existent. Who are you? A detective? That's the farce. Its blank non existent. What you are you hold within. Not what you show and let others perceive of you.
PS. Well, at least I managed to write a big mess.