Bromelain is good for dissolving scar tissue.

I don't know how brave you are, but I saw this where components of bee venom break down scar tissue:

"Bee venom therapy is often used for inflammatory conditions, such as bursitis, tendonitis and arthritis.

This is because bee venom is packed with powerful natural bursitis healing substances, enzymes and peptides, including:

Melittin

Stimulates the production of anti-inflammatory steroid cortisol
100 times stronger than (hydro)cortisone in conventional drugs
Adolapin

Anti-inflammatory
Pain-blocking analgesic
Formic acid

Antibacterial, anti-inflammatory
Warming
Helps joint stiffness and weakness
Widely used in Arthritis treatment
Also found in nettle plant


More than 40 other active chemical components have been found in bee products and these act together to:

Boost immune system
Dissolve scar tissue
Suppressed the erosion of joint cartilage
...and much more..."

http://www.mybursitis.com/bursitis-apitherapy.html

Serrapeptase, Nattokinase and Lumbrokinase might be helpful but not really directed enough when taken orally. Using DMSO on the skin would be helpful but needs to be handled carefully because it is a solvent which causes anything on the skin to enter into the skin. That includes bacteria and anything else on the skin. Therefore the skin would need to be cleaned thoroughly and the area sterilized before using DMSO. Do not use a finger to apply! Use some other implement such as the handle of a sterilized spoon or something like that. Combining DMSO with the previously mentioned enzymes might be helpful. However start very slowly with tiny doses to check the effect.

Vitamin C would be helpful and so would the amino acids needed for collagen formation. Making a salve using these might be helpful. DMSO would force them into the skin but combining all of this is difficult as I have tried DMSO gel with vit c and amino acids and it became liquid which runs off the skin.

Iodine is meant to be effective too. Lugols stains so potassium Iodide might be worth trying if the skin area is visible as Lugols would stain brown.

Lugols 5% liquid Iodine is the gold standard for removing scar tissue, or lesions.

I removed a terrible looking skin lesion with iodine, and fresh new skin was the result. You can't even see that there was a lesion there, except the new skin does not match the color of the old suntanned skin. I carefully applied Iodine to my lesion 2 x a day, every day. The lesion soon formed a scab within a few weeks and after about 1 month the scab started itching & fell off leaving fresh new skin. Do not pick off the scab until it is itching.

Do a google of "Iodine Scar Tissue" for much more.

I suggest practicing the procedure on a small spot before doing it all.

Grizz

Serrapeptase is good for scar tissue. Take it twice a day on an empty stomach.

For internal scar tissue, I am not sure... I though serrapeptase would be the answer, but other replies say not so... for external scar tissue, check out a product called biosil. It has had independent clinical trails (randomized, double-blind, placebo-controlled, parallel group) that show very good results.
These are the studies below.
Barel et al 2005
Wickett et al 2007
Spector et al 2008

Its a product from Belgium that is used for bones, and skin to increase collagen, for hair, skin and nails but also bones.

I am not sure but if you use this product in conjunction with a strong dose of vitamin C (to mediate the collagen and help it regenerate), then it very may help reduce the scar. If not, then at least you will have lovely hair, nails and skin. I use it and its quite good. I have noticed tauter skin all over my body, and more radiance.

But then again scars are funny. I have had some very small ones for 26 years from when I was a toddler. Yet some people can fade very large ones. I think it is genetic.

If it is internal then I would love to hear back as to what can do that!

All the very best!