In his prime, The Terror was a force to be reckoned with, being responsible for the deaths of various heroes and was able to evade capture many times. However, he's so old he's not able to pose much of a threat anymore. Still considering his reputation in the past, he is still not someone to underestimate and is still feared to this very day.
The Terror vs. The Tick
He's Barry's old nemesis. Barry tricks him into thinking that he's changed his costume to blue and has a new sidekick, so The Terror now thinks that The Tick is his old nemesis.
However, The Terror appears in later comics, so he apparently survived the attack.