The meaning of 切る on the end of verbs


Is there a general meaning for `切る` on the end of verbs?

I think it might have to do with "completely doing" something. If that's the
case, how does `～切る` on the end of verbs differ from `～てしまう`, for example how
do `成り切った` and `なってしまった` "turned completely into" differ in meaning?

Additionally:

  * How does the meaning of `支え切れなくなる` differ from `支えられなくなる` "become unable to support"? Can `支え切れなくなる` mean "will go past the point of being able to support"?

  * How does `疲れ切った` differ from `疲れた` "exhausted"?   
Does `完全に疲れた` "completely exhausted" have a similar meaning to `疲れ切った`?

  * What is the relationship between `割り切る` and `割る`?



  1. Yes. The meaning of `きる` common to those examples is to `complete doing ...`.

  2. `てしまう` does not necessarily mean `complete doing ...`. So they are different.

