TMI was an event that was wholly contained within the containment structures, and was due to human error.

Chernobyl was a combination of human error and failures to understand events as they were developing, plus flaws with the design of the reactor - to say nothing of the lack of a proper containment structure.

Fukushima Daiichi was the result of a massive quake and tsunami, combined with poor placement of backup generators and the inability of TEPCO to understand what was going on with the reactors in a timely fashion.

The new reactor designs are supposed to be built with redundancies, including shielding and backup water that is gravity fed so that no pumps are required. That would allow operators to put water on the reactor in case of a problem with the core and control rods to cool it down.