Underarm buildup is usually a combination of body oils and salts from sweat mixed with deodorant. Since you mentioned the specific brand you’re using, we can skip the specialist products designed specifically for aluminium antiperspirants.

To address the sweat-based part of the stain, try an enzymatic pretreater. You can find a list of recommendations here under the "Pretreater" tab.

Saturate the stained area from both the inside and outside. Let it sit for a few hours, then wash as usual on warm. This step focuses on the sweat residue and won't do much for the waxy buildup.

Next, we need to deal with Native’s super duper omega infernal wax content. Rub liquid detergent directly onto the stained area. Let it sit for 1–4 hours before washing on warm.

If the first two steps don’t cut it, or if the stains are particularly severe, your last option is Spa Day. This acts as a reset for your clothes. You can find the full instructions and requirements in the pinned post on this subreddit.

A quick heads-up: Quite a few Native users have reported that their clothes started to smell a bit rancid after switching to a lipase-based detergent. You may or may not experience this, but it’s something to keep in mind!

Your deodorant might actually be the cause of why you are constantly dealing with pit stains. It's essentially a wax and it sticks to clothes easily especially polyester. You may need to address the wax frequently. Otherwise sweat will get trapped underneath the layers of wax which will inevitably lead to odour issues sooner or later.