For the entirety of East Blue saga, Nami is among the fodders of the One Piece verse. However by the time of Baroque Works Saga, with the introduction of her signature weapon the Clima Tact (party version) elevated her from fodder-hood. Only in the hand of Nami that such a ridiculous weapon could be lethal. On her first trial she defeated Miss Doublefinger, a high ranking officer of BW. At first, it was the weapon's surprise factor that catch her opponents off guard. However, by the time of Skypiea Arc, she was so proficient at the clima tact that in my opinion she could handle Miss Doublefinger again without the surprise element. As proof to this, her most major accomplishment up until that point was stalling the all mighty God Enel.
After Usopp upgraded the Clima Tact with dials, Nami became a serious threat in the lower/mid tier. For the first time in the series, there is finally a weapon that has the capacity that can exploit Nami's talent of weather perception to the fullest. Mirage Tempo helps her cloak herself from the enemies with clones. While the various Thunder tempo and Cyclone tempo are capable of hurting even the monster trio. Nami's most triumphant preskipped moment came in the defeating of Kalifa of the CP9, whose strength was the equivalent of 63 marines. The battle proved how destructive Nami's weapon could be by breaking through the super human defense feat known as Tekkai.
Since then, Nami is much more involved as a combat member of the Strawhats helping to fight foes like the Flying Fish Riders, Oars, and or the Pacifista model PX4/PX1.
-Defeating Miss Doublefinger with Clima Tact
-Defeating Hotori/Kotori with Gan Fall
-Stalling God Enel
-Defeating Kalifa with perfect Clima Tact
-Involved in battle with Flying Fish Riders, Oars, and Pacifista
Weapons: Perfect Clima Tact
-Mirage Tempo to cloak herself with clones
-Cyclone Tempo (various)
-Thunder Tempo (various)
Other Strengths:Average human physical, keen weather perception, 3rd most intelligent in the East Blue Saga