great Avenger for solo play, taking a standard 3 per player side scheme is fairly easy to get rid off for justice, triggers skilled investigator etc. also has great stats for Justice which lack dmg - 3x 5 dmg activations is just great for 3 cost.
in 3-4 multiplayer not that great when suddenly the same standard side scheme becomes 9-12 thwart... still its playable if one wants to have a side scheme in play, but one way or another gives possibly greater benefit then Sentry.
please remember to count side schemes in Villain deck before you play him - you might find 6 additional threat on main scheme fairly unpleasant :P if you dont find a side scheme.