Original Wording

The Second Horseman: War: Modify Hulk’s attack value by +1 until the end of the turn for each opposing character who took damage from an attack this turn.

Here’s Your Friend Back: Give Hulk a close combat action that deals no damage. If it hits, place the target in a square adjacent to an opposing character who is within 10 squares and line of fire. Then make a ranged combat attack against that second opposing character, even if that attack would normally be illegal. If this second attack hits, deal both characters 3 penetrating damage.

Brainwashed: Friendly characters may target Hulk with Mind Control.

Errata

Here’s Your Friend Back: Give Hulk a close combat action that deals no damage. If it hits a character, place the target in a square adjacent to an opposing character who is within 10 squares and line of fire. Then make a ranged combat attack against that second opposing character, even if that attack would normally be illegal. If this second attack hits, deal both characters 3 penetrating damage.

Does Brainwashed allow a friendly character to use Mind Control even if they do not already possess/use it?
No. It changes who a Mind Control character can target. It does not change who can use the ability. To see how a special power might allow another character to use a power they normally can't, see characters like Mr. Miracle/Oberon.

Can Hulk throw a character with Here's Your Friend Back adjacent to an opposing character using Stealth?
No. Hulk needs to be able to draw a line of fire from his current square to the target opposing character (within 10 squares). That would be before you remove the adjacent opposing character. Once you identify the opposing character, THEN you place the adjacent character next to the target (in any square that's adjacent to the target) and you make the ranged attack.

Can Hulk use an object, blocking terrain or wall as "the friend" and attack someone 10 squares away?
I suspect that is not the intent. I need to get an answer from WK to be sure. A draft of errata is posted accordingly.

Updated (filler)

Updated to reflect errata.