Jenova as in FF7

[spf1200]

The worst = bottom of the list, the singular worst.
One of the worst = one of several at the bottom end but not necessarily the one AT the bottom.

One could consider VII 'one of the worst' FF games but it actually be the fifth worst if they listed them all out.

Both sentences condemn the thing for being bad, or at least, of comparatively lower quality than most of the overall group, but there is an important difference.

Please read this OP and learn how the English language works, I know it can be hard but please do try