The overall violence is very occasional. It is more about the consequences of a science experiment more than the grotesque sequences.
R violence type: blood and gore.
During a sequence in the first half of the film where the main protagonists have just had sex, a computer chip becomes stuck on the man's back, making him jump in pain. The woman gently peels it off him and we see three small, bloody cuts on his skin. This is shown in a close up and lasts for a brief second.
A baboon's skin is turned inside-out. It can be seen squirming and screeching in a pool of blood.
A man arm-wrestles another man before breaking his arm so that the bone protrudes from the skin. Some blood shown.
A man peels off his fingernails. Blood is not shown, but a pus like substance is secreted.
A man's ear falls off. There is no blood.
A man vomits white milky enzymes over a donut.
A woman has a nightmare about aborting a giant maggot. It is covered in blood.
A man's teeth fall out. He then places them in a collection of other detatched body parts.
A fly creature has its jaw torn off, and its human eyes fall out, including its outer skin until it transforms. Almost no blood is shown though.
Deleted scene includes a horrific cat-baboon creature to attack Brundle-fly, it scratches a big open wound on his back (no blood). Brundle-fly then beats the creature to death with an iron pipe, some blood.
Another deleted scene includes a fly-like leg emerge from Brundle-fly's torso, we see it penetrating through his skin. Brundle-fly amputates it, first ripping and finally biting it. We see some veins and skin torn apart.