Well, the best armors in the game would be the PvP sets (Statius and Vesta), but disconsidering those, the best set will depend on what your stat priorities are:
Head: Dragon full helm (for defense), Helm of Neitiznot (similar defense to Rune full helm but has prayer and strenght bonuses, and no negative bonuses)
Neck: Amulet of Fury
Body: Bandos Chestplate
Legs: Bandos Tassets
Feet: Dragon boots
Shield spot: Dragonfire shield (very good defense with 7 strenght bonus) or Elysian/Divine spirit shields (No strenght bonus but they have nice effects, look that up on RS Wiki) for defense, rune defender for a decent defense bonus with the benefit of attack and strenght bonuses also.
Weapon: Abyssal whip or Godsword, depending on your playstyle (if you like a faster but weaker, or stronger but slower weapon). The whip becomes especially good with the added +19 slash attack and +5 strenght bonus from the rune defender.
Cape: Fire cape
Ring: Ring of wealth for extra chance of rare drops, or Berserker ring for strenght bonus.
Hands: Barrows Gloves from Recipe for Disaster
That's basically it.
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