Best place,monster,or something to train 90-99 Strength runescape?

I suggest bandits because they're really easy to afk, or Monkey guards on Ape Atoll (It's right beside an altar too, so you can protect melee, and keep praying whenever it gets low, and you won't have to worry at all about getting hit!) But if you use the Money Guards way, bring a few anti poisons because really annoying spiders spawn, and poison you.