So im thinking of creating a runeblade fighter and was just wondering what thoughts were on if you think its any good and some cool rune combos to choose as i move through the class. i definitely want to be more tanky but im also considering just a great damage dealer. also if you want to throw out any fun ideas for the backstory or how it was found thats great too!

Goliath race. Hill and fire runes, they help with being a tank. Maybe frost rune. Backstory: grew up learning how to control the magic of runes, learning from a master in their tribe. Then, their tribe was attacked. They were one of a few survivors. Ever since, they have been searching for the killers, using the magic of runes to destroy their tribes killers. There you go. 

I have a warforged Rune knight in the works, he is fire rune and storm rune.  I think of them as enhancements to his processor.  Good with tools from fire and the shackles are his method of restraining people.  The storm gives him more data storage on magic, and the ability is him overclocking to predict and influence the flow of battle.  He also is currently working as a bounty hunter and usually brings them in alive, with the fiery shackles and using the giant ability for advantage on grappling checks.  I have him multiclassed with rogue which gives him thieves Tools and he has tinker tools for three tools with essentially expertise.  

Many of my goals involve restraining enemies and pummeling them while in my grip.  I am taking grappler when I can for added bonus.  But with rogue I already have expertise in athletics so things aren't getting away from me very often.

If Duergar is allowed in you're setting they're a very fun option for Rune Knight. The story of Duergar can easily vary setting to setting, if they're still typically evil underdark peoples then they could have an alliance with the Fire Giants. Maybe they're not so evil and your clan/family found refuge in a long-dead master workshop of an ancient giant of legendary skill and are only just now learning to replicate their work (that idea would work for any race). 

Anyways, why Duergar? Because you can become HUGE. Once per day Duergar can cast enlarge on themselves as am action. Meaning Rune Knights can make themselves large with a bonus action, then cast enlarge to make themselves Huge (20ft by 20ft of meaty dwarf, +1d6 & +1d4 to your damage, literally pick someone up in your hand and throw them). Woe to the first foolish bandit who makes fun of you for being 5ft tall.

I didn't realize it till afterward that I am halfway between robocop and the terminator for my warforged.  Probably playing it up as a manufactured weapon from who knows when (his internal memory storage got damaged while he was deactivated) at least he knows his name.  V.U.D.U. Variable Utility and Defense Unit.