Aggressive is really exciting when you have an amazing team that works together... or if you want to go faster and have a really fun time even with level 1s (serious), just do the Duggen Shipments mission.

Start an MC Club to allow up to 7 people to join you in the fullest lobby you can find (Start --> New Session; etc) and then wait till you have 2-3 or more people. Do the Duggen Shipment mission with a jetpack or a plane (or anything that can fly and shoot at the same time, MK II; etc).

That in itself is fun, just knowing that every 3 Shipments you destroy weakens the staff. If you get 7 or more, you will be able to do the heist with the weakest 5% guns (Mini SMG / Machine Pistol) and still dominate.

Total domination with the guards with weakened Duggen Shipments with low levels (or any levels) is hilarious and fun how fast it goes and aggressive you are.