60 E Hawkeye
50 V Lizard
23 E Destiny
83 U Nightcrawler
27 E Moon Knight
46 V Black Panther

Total=289/300

Hawkeye-just use him as a sniper. pretty happy with his performance.
Lizard-My 2nd muscle of the group.
Destiny-Probability Control.
Nightcrawler-Main attacker.
Moon Knight-Super strength for cheap
Black Panther-Cheap outwit and can hold his ground.

If you're happy with the way the team runs, an obvious fix would be to raise Destiny to the Veteran version for only 6 more points. This would raise your point total to 295.
Or are you trying to low-ball your team build total?

I would like to add someone with leadership but try to keep it at 300.

Get Black Panther to R and put in a R Sidewinder....

Updated Team:
83 U Nightcrawler
60 E Hawkeye
50 V Lizard
27 E Moon Knight
27 R Black Panther
24 R Kingpin
23 E Destiny

Total=294/300

You could get E Kingpin for 29 points instead of the R, raising you to 299. As has been mentioned, Sidewinder is a Leadership piece that fits in at the same points-per-level as Kingpin (although with less clicks of Leadership). And if you're okay with mixed Universes, you could get R Aquaman for 27 points, and have a Leadership figure who might make a big difference in combat (3 damage + SuperStrength)

im using r kingpin b/c thats all i have and i dont plan on attacking with him. I also want to keep my team all-Marvel.

I'm guessing you don't have V Destiny either? That would add 6 to your team value, bringing you up to 300 even. Alternately, R Scarlet Witch also costs 29, has the same number of clicks of PC, the same free move, an extra click of life, and may even be able to deal out damage in a pinch.