Cannon Main + Witch + Shaman.
This mission introduces Boats, something you might not enjoy having to ride on in this game. Also there's a shortcut trick here so you wouldn't have to kill as many mobs as you would if you follow the preset objective sequence.
Destruction of enemy supply routes while eliminating the enemy force one group at a time is what's demanded to be able to solo this mission. And as usual for low level TBSs, a Witch is required if you have low gears like the stuff used here.
Witch makes low level TBSs a lot easier even if you don't have very good gears so I'd suggest getting one unless you have high-end mercs such as Sheriff or gears that can 1-hit level 70 TBS mobs in this case.
This makes a good introduction to TBS missions. Since most new players at level 50s would only have D class mercs, I used those for this demo.
If you're new to TBS missions, you would want to familiarize yourself first by running them with 2 or more people. Although this demo is solo, it should be enough to show you how it's done.
Ranged mercs work well in this mission, particularly with Hwarang's Aura since you'd want to destroy a Summon Gate fast at one point.
There's also a crapload of traps to deal with although you only need to remember the 5 Net Traps at least.
Learning to solo Last Stand can be a very exciting adrenaline rush experience at first. With the mad dashes to destroy and kill stuff at two locations simultaneously within a limited time to be prepared for the next timed events.