Blasting, pummeling images of war, its dead and dying clutter the screen. And because of the looping/time-travel conceit, some characters particularly Cage and Rita are seen being killed over and over again, each death a slight variation of the last.
In one scene, a character's face is seen melting for about 3 seconds. Mild gore is shown briefly.
Those deaths are mostly bloodless, but include percussive explosions, impalements from creature tentacles, and images of our heroes being strafed by shrapnel and banged by large mechanical devices and vehicles. A number of times we see Rita lying prone, dead with a glazed-over expression.
As Rita quickly tries to train Cage and bring him up to speed as a soldier, he's heavily battered. In each case it's recognized that Cage must "die" in order to restart the day and thus get on with the important training process, so Rita casually shoots him in the head whenever he's hurt. (We generally see her point the gun at the camera and pull the trigger, which cuts to Cage waking up on the same day.)
Quantities of people die in huge explosions. A guy is crushed (several times) by a gigantic crashing transport plane. An airborne transport ship blows up in repeated loops, burning soldiers and sucking them out through a hole torn in the craft's side. Swirling tentacle creatures (called Mimics) grab and throw men and women around like crumpled wads of paper. A man detonates a Mimic with a Claymore land mine held to his chest between them. Two soldiers use a Claymore to destroy a fuel truck, enveloping themselves and a number of the aliens in an eruption of flame and shrapnel. Machine guns and RPGs do their share of damage. A man is knocked out by a Taser and run over by a truck. A woman wields a large sword, using it to hack into the Mimics on a regular basis. A man is dragged a long distance, dangling outside a fast-moving craft by one arm.
Near the end of the movie, a woman is mauled by a mimic. A split-second shot of unidentifiable bloody body parts the creature is holding suggests that she has been literally torn apart. Due to the lighting and quick-paced sequence of shots, this is not very visible though.