Shooting me in the head with a ten gauge slug will piss me off just as badly as if I was shot with a 9, a 40, 45, probably even 10.
We have rounds available from short rimfire to the nitro express rounds. Every purpose has an assortment of calibers that are useful, and some that are optimal. With all of the different concerns,benefits and drawbacks, there's no such thing as perfect, it's kind of hard to even think that way for me.
Btw, one of the words that really annoys me is "overkill". People throw that out when someone uses more force than they themselves think is necessary, such as the guy who uses a .223 for deer declaring that the 45-70is "overkill."
Dead is dead, and what matters most is incapacitating a threat. If it's not safe to use a .45 in a crowded mall, then it's not optimal, but it's not "overkill.".
Overkill is a .220 swift on a prairie dog the size of squirrel.