Just a short question about 6 drop captain america.
So w/ this effect, my opponent has cap in the support row w/ Doc Samson, Agent of S.H.I.E.L.D. in front, If I attack samson and he exhausts cap, what happens
1) does samson take breakthrough but no stun damage due to the effect or
2) nothing, no stun no damage

we went w/ #2 after much debate, a clear answer would be appreciated. Thanks.

The key word is "instead"
So instead of stunning damage, you exhaust Cap and Doc isnt stunned. Breakthrough still applies as normal.
Cap with his shield that allows him to ready is just a huge pain for the opponent...