I am not a fan of AK off-suit pre-flop. I like to limp or call pre-flop depending on my position. I will raise preflop minimum, if:
1) There are no previous raises.
2) Most of the players have folded.
3) I'm in a late position.
Then, I like to check the flop(like the Hero), or make a minimum raise to gauge the other player. If they go all-in on the flop, then, they could easily be representing and over-betting and trying to steal the pot (depending on what stake or level the blinds are at, the cash game or tournament's average chip stack size, the V's chipstack size, and my chipstack size.
I wouldn't use auto-fold ever really unless you're trying to take a break from playing for a minute or an orbit or two.
Otherwise, if the player ships it there on the flop and you don't think they're representing, then they very well could have Trips (A's, 10's, or 8's), an open-ended straight with a diamond flush-draw and top pair or a pair; Or, they might just have two pair (A's and 8's, or 10's and 8's). The only way to get a better read on the player to know what they might be playing, is to have already put them on a range by seeing them in action/playing previous hands with yourself or others at the table during your session.
But seeing as you don't have any diamonds on your AKo, there seems to be a lot more that could go wrong then good by making that call... You'd basically be looking for another A to pop out on the turn or River, or a King to pop out, or runner-runner Q-J (with no diamond)
I probably would have folded in this situation after some thought, unless i had my opponent heavily out-stacked and could afford to call if i was unsure about what he had and wanted a better idea of what they could be going all in with for future reference against him or other opponents in similar spots.
Also, it depends on what you raised to pre-flop, it could have been an improper or bad raise, and your V could be in there with J-9 (offsuit or suited)
Or if it was a proper raise, but youve been playing alot of hands, then they could actually have a really good hand like A's or K's.
Or they could just be calling you bc you've been playing alot of hands or giving alot of action.
Or they might be calling you because they see you play alot of hands, you raised it for them to a healthy amount, and now theyre trying to slowplay or trap you, but suddenly changed their mind on the flop, and trying to steal the pot..
hope this helps lol
GL!!!!!
)))