Ace: Island level+ (6-C), matched Aokiji's ice with his fire and survived a clash with Akainu who has a superior Devil Fruit with no serious injuries.Jozu: Island level+ (6-C), made Aokiji bleed and is comparable to Ace.
Marco: Island level+ (6-C), took hits from Garp and Akainu. Comparable to Ace.
Vista: Island level+ (6-C), kept up with Mihawk in a brief fight. Comparable to Ace.
Doflamingo: Island level+ (6-C) higher with Awakening, broke out of Aokiji's ice with no side effects and took hits from Gear Fourth: Boundman Luffy who should be much stronger than Jozu.
Tsuru: Island level+ (6-C), Doflamingo feared engaing her in combat during his time as a pirate even well she was past her prime.
Jinbe: Island level+ (6-C), matched Ace in combat for 5 days. Blocked attacks from Akainu and Big Mom.
Blackbeard (Pre-timeskip): Island level+ (6-C), nearly broke Ace's neck with a single attack.
Cracker: Island level+ (6-C), capable of injuring Gear Fourth: Boundman Luffy.
Smoothie: Island level+ (6-C), stronger than Craker.
Katakuri: Island level+ (6-C)possibly higher, stronger than both Cracker and Smoothie. Took hits from Gear Fourth: Boundman and matched Gear Fourth: Snakeman when Luffy had become much stronger.
Jack: Island level+ (6-C), should be comparable to other Yonko Commanders. Survived an encounter with Sengoku, Tsuru and Fujitora with no serious injuries.
Zunisha: Island level+ (6-C), one-shot Jack.
Nekomamushi: Island level+ (6-C), held of Jack for 5 days well taking 12 hour breaks after 12 hours of fighting.
Inurashi: Island level+ (6-C), held of Jack for 5 days well taking 12 hour breaks after 12 hours of fighting.
Jesus Burgess: Island level+ (6-C), should be comparable to other Yonko Commanders.
Sabo: Island level+ (6-C), defeated Jesus Burgess with relative ease.
Dressrosa Saga Luffy: Island level+ (6-C) with Gear Fourth higher with strongest attacks, casually broke Doflaingo's strings by transforming which could restrain Jozu and break out of Aokiji's ice. King Kong Gun one-shot Doflamingo through his strongest attack and defense although both where seriously injured.
Whole Cake Island Luffy: Island level+ (6-C) with Gear Third possibly Large Island level (High 6-C) with Gear Fourth higher with strongest attacks. Comparable to Katakuri with Gear Third. Gear Fourth: Boundman is stated to be several times stronger than Luffy's strongest attacks by Doflamingo. Tankman and Snakeman should be comparable. One-shot Cracker and several biscut soldiers with Tankman: Full Version, King Cobra defeated Katakuri and caused him serious damage.
Whole Cake Island Luffy can change depending on how we decide to scale him.
Edit: I added a few characters I forgot. If I missed anyone please add them.