hello my name is orangecat241 I am a silver 4 gnar one trick you have probably seen this guide before it was around 8.20 but then I archived it now I am reworking it for you gnar players out there.

[Orangecat241 approved]:
the runes I personally take they are very good for sustain and poke and I personally prefer. Grasp is very good as it can help you sustain. the demolish for splitpush,second wind for sustain and overgrowth for tankyness. then you want to go into the precision tree for alarcity with the attack speed and coup de grace for the damage. For the stats the attack speed one is essential and the best for gnar the second one could be armor or magic resistance (look at their comp.) lastly health for well tankyness.

[sustain]:
First fleet footwork witch helps with sustain cause it heals,triumph for teamfights and ganks,alarcity for attack speed and coup de grace for damage. With resolve secondary you should take second wind and overgrowth for sustain and tankyness these runes work best with dorans shield.
stats:
attack speed (essential.)
armor or magic resistance (interchangeable.)
lastly health (essential.)

[the cat partners with a cat]:
This one got nerfed pretty good but it is still viable.
summon aery for poke,nullifying orb for survivablility,absolute focus for the bonus damage you get when you engage with high health and scorch for poke and fights.
Resolve secondary should have second wind and overgrowth for sustain and tankyness.
stats:
attack speed...
armor or magic resistance...
health...

Gnar is great for team fights and laneing because he his combo can destroy enemies
in the matter of seconds also he can poke enemies out of lane.

start: dorans blade is the perfect start as it offers sustain and great stats for Gnar. Dorans shield can also be an option if you are getting poked

first back: can be a jaurims fist,phage,bramble vest or spectres cowl
just buy depending on situation so jaurim for normal,phage for BC rush bramble or spectres for AD and AP respectively.

full build: the frozen mallet is a huge item for gnar nice stats and passive for chase and kite,boots for situation,black cleaver for the powerspike and stats. Deadmans plate for tankyness and extra chase and damage. Spirit visage for tankyness and extra heal when going mega. thornmail for pure tankyness.

level1: Q good for poke and farming.
level2: W good for poke and fights.
level3: E good for engage and escape.
level4: Q more poke damage.
level5: Q even more poke damage.
level6: R main combo power.
level7: Q super poke and fighting power
level8: W helps fight more and kill faster.
level9: Q ultimate poke and fight damage.
level10: W super fight power.
level11: R more combo power.
level12: W super pooper fight power.
level13: W maxed for super fighting power.
level14: E engage and escape.
level15: E can offer more engage and escape.
level16: R super combo power.
level17: E last ability to max.
level18: E super powerful engange escape.

flash: essential cause it is flash helps escape make plays etc.
teleport: helps you splitpush engage help team or get back to lane. Ganks.
ignite: wining lane easy kills etc.

gnar is a very good champ for team fights and it very decent in lane being able to survive tower dives (if in mega) and turn the tide of a game. with is ult he is a very good champ but not really meta right now.

Gnar can be used to climb with but is not the best as he is hard to carry with as if your team does bad he probably will too bruiser are probably a better option.

in game:
pros:
-great for teamfights.
-can burst with combo.
-great escape.
-mini is a great marksman.
-mega great tank.
cons:
-can be killed easily without team.
-lots of requirements for combo.
-easily beaten by bruisers.
-mini vulnerable.
-mega can be shredded.

mental:
pros:
-variety of builds
-unpredictable
-great outplay potential

-cons:
-clashing build with character.
-hard solo carry potential.
-difficult champ.

make sure you have enough rage before the battle get at least one or two w procs as mini gnar
E into mega ult enemies into wall w them q and just start fighting your team should follow up on the stuns.
before fights attack camps in jungle to get enough rage for fight.

p***ive: rage gene
his most unique feature it basically makes you transform into mega once
your rage bar is full also he is more speedy and attack speed like in mini and gets tankier
stats in mega.

Q boomerang throw/boulder toss:
basically mini gnar throws a boomerang and it slows enemies and damages them once hit it does half damage if hit on the way back(can only hit once) and if you catch it the cooldown it reduced. for mega gnar he tosses a boulder which damages and slows enemies
if you pick up the boulder it reduces the cooldown.

W hyper/wallop:

basically for mini gnar he has this ability where if gnar hits an enemy with three abilities or attacks they take magic damage based on 6% of gnars max health also he gets a decaying speed boost. He gets a passive where if he exits mega gnar he gains the decaying movement speed. for mega gnar he slams the ground in the area of choice stunning enemies
in the area.

E hop/crunch:

basically mini gnar hops to the area in the radius if he hops on any ally he does a double jump extending the distance if he hops on an enemy he gets the same increased distance but will also add a stack for his w. for mega gnar he hops at a location damageing and slowing enemies in the radius if he uses this ability while about to transform he gets the bounce off mechanic of mini gnar while having the slow and damage of mega gnar.


r GNAR!!!:
gnar throws enemies in the direction of choice airborning them if he throws them into a wall they will be stunned for a bit (ONLY MEGA GNAR CAN USE THIS)

last hit minions and poke with q until level 2 where your pokes will be better also once you hit level 3 you can start engaging some matchups you will have to start engaging at level 6 or only if the jungler comes to help.

use q to clear along with basic attacks.

mini:
AA->Q->AA
Q->AA->AA
E->AA->AA->Q

mega:
start of mini: E into mega->R->W->Q
already mega: E-R-W-Q
flash->R->W->Q->E

Malphite: in progress...
ornn: in progress...
amumu: in progress...
blitzcrank: not started.

gonna add color text and images/videos.