How can I get rid of these under arm scars from shaving? (Photos)

Axillary hyperpigmentation responds well to Luminase and Exfolase creams to reduce the discoloration. If this is genetic, you may need several months to see longterm results. Best, Dr. Karamanoukian

Hyperpigmentation from any type needs a combination approach of peels like cosmelan, lasers like clear and brilliant and aerolase or laser genesis, radiofrequency like venus viva, and constant skin care and sun protection. I suggest a formal consultation with an expert in lasers and peels. Best, Dr. Emer.

The darkening is from post-inflammatory hyperpigmentation. I would consider laser hair removal first because if you continue to shave you will continue to cause further darkening. Time alone will then lighten your underarms but the lightening can be augmented with peels and/or hydroquinone. I would certainly avoid IPL.

Thank you for your question and posting pictures.  It looks and sounds like you have post inflammatory hyperpigmentation.  Since you are a Skin Type IV-VI, we would not recommend any IPL and some other energy treatments for you. 
We have been very successful using the PicoSure laser with the FOCUS and / or Flat Lenses eliminating hyperpigmentation with a series of treatments.  FOCUS lens treatments have the extra benefit of reducing fine lines, wrinkles and scars.  This is one of our go to treatments for patients older than 40 and worried about the signs of aging.  This laser is safe for all skin types.  Start with sunscreen every day!  Once you have treated your hyperpigmentation to your satisfaction, you will probably need a follow treatment every 6 to 12 months depending your level of re-pigmentation.  Best of luck.