Key to tenderizing is acid the enzymes will breakdown connective tissue. Ie of acids citric acid from the likes of lemon, oranges, pineapple, kiwi, papaya, etc, vinegar, wine, tomato, buttermilk and such. The problem with any acid it must be balanced with other ingredients to not over power the flavor of the finished product. Be it water, oil, beer....so on. The meat needs to be in contact to be effective, I like using a large ziploc and kneed it periodically to ensure the marinade is evenly distrubed amongest the meat.

My venison marinade consists of a cup of olive oil, 3 tbs of soya, 3 tbs of lemon juice, chopped garlic (I like garlic so like 6-8 toes), tbs of chives, parsley, thyme, oregano, rosemary(if you like), onion powder(not salt), paprika, pepper or steak spice. Secret ingredient is maple syrup, while I prefer the real thing pancakle syrup works just don't use butter flavored...yuck! I usually put in 2tbs but 3 works for a sweeter finished product. Mix marinade add meat, kneed then refrigerate for 24hrs. Kneed periodically. Prior to cooking I remove the ziploc for an hour so the marinade un solidifies some. Hot grill few minutes a side, plate and rest with foil tent for 10 minutes. Med rare result.

I know guys who use coca cola, italian dressing, etc for the marinade, then simple season prior to grilling. I personally use seven up, Worcester, lemon juice, garlic and pepper for chicken to create my own teriyaki.

Another way to tenderize is with a tenderize mallet, to create fried steak. Can be pan fried or breaded. Make a rue and some fry some onions..gtg.

Fridge aging is also an option for a tough animal, simply place the meat on a paper towel on a plate, meat and another on top then refrigerate. Change the paper towels often, or once blood soaked. It will blacken over time due to cool air touching the exposed areas but it cooks fine. If bothersome you can remove that layer.

If you google venison marinades, tenderizing or aging you'll find a lot of opinions.

Good Luck