Because when Clark gets angry he loses control, which means he loses that thing he loves to do so much, holding back. Clark not holding back is far more likely to kill, not with intent but purely because when you are truly angry, you don't care. And when your Superman and have no control over your power, bad things happen.
Re: SPoilers for UK people or people who didn't last thursday's episode.
Its the attitude and the lack of inhabitions.
Which is why I find Clark on red kryptonite much more interesting and fascinating than the normal boyscout, mr perfect, to good to be version.
I just hate how perfect they make him out to be allot of time. Mostly in the comics and movies. Actually what really got me into Smallville was when he didn't save Alicia. I true started to find interest in the show and respect it because that was the first time I ever saw Superman lose. Thats always been the thing that never allowed me to like the character as much as I want to. The guy never loses and never really has any problems. He has everything anyone could ever imagine just handed to him and only has pretend BS problems that are truly just crap. When I saw him find her in the barn dead thou, I really respected the show for that. I could see so much pain, real pain, inside him then.
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