Some scenes involve torture, especially the latter half of Season 2 which is significantly more dark than most of the series, including a character being punched, whipped (with bloody results), and beaten with a metal pipe. Despite this series having very little blood, some of the fight scenes can be quite brutal and hard to watch.
Frequent martial-arts 'esque fighti scenes are depicted throughout the series. A lot of hand-to-hand combat (including use of weapons such as knives) scenes are also depicted, but these scenes lack blood and gore. When guns are involved, it's slightly more graphic. But it never gets high enough to level with shows like Fringe or NCIS. Some explosions, car chases, car crashes, etc. Despite the dead bodies depicted in the series, it never lingers on them or shows graphic and bloody details.
[Season 3]
Season 3 has more action sequences than Season 2.
Almost every episode has at least one fight scene. However, these scenes tend to be short and milder than Season 2's fight sequences.
Most sequences involve fast-paced kicks and punches where the bad guys are quickly taken down. These create the excitement and entertainment without escalating into threatening content for younger viewers.
[Season 4]
There are some scenes of mild violence, in the form of hand and leg combat, and gun shooting with little bloodletting.
[Season 5]
In each episode, the main characters have to fight against various villains, such as spies from other agencies. These combat sequences depict either hand-to-hand (melee) fighting scenes between the characters, or gun battles that contain realistic sound and visual effects. However, these combat sequences are brief and do not contain details such as blood.