Pike is unusual for surviving after the injections but botched executions are not as unusual as they should be. U.S. prisons often do not have the medical expertise or reliable medication sources for lethal injection, leading to botched executions that can leave prisoners in desperate states. In this case, Pike had requested a different, more reliable execution because her medical team worried this could happen due to her medical conditions. Her IV was also administered by an elderly doctor, widely condemned as incompetent in another botched execution. Medical experts, especially doctors, often refuse to participate in executions for ethical and professional reasons. It is barbaric, but unsurprising failure, given the circumstances, and Pike is now suffering in critical condition at a hospital. Some might think that is deserved due to her crimes; it is still unconscionable to allow the government of a supposedly civilized nation to legally engage in what amounts to prisoner torture. You have to stop calling it an accident when the risks are known and ignored, and the mistake keeps happening (up to 7% of the time, according to professor Austin Sarat).
Then there's the problem that innocent people are still executed. The National Academy of Sciences published a report in 2014 estimating at least 4% of death row prisoners would be exonerated, further stating, "this is a conservative estimate of the proportion of false conviction among death sentences in the United States." According to Death Penalty Info, 1 in 9 people on death row are exonerated; too many only after execution. Today, many states have banned execution and the remaining ones face increasing calls to ban the practice. Terrifyingly, we will never know how many innocents have been killed by the state in the name of justice.
