be the person to suffer the most (as the result of an attack,
The origin of brunt is unknown and may be onomatopoeic. The sense has evolved from the specific (a sharp or heavy blow) to the more general (the shock or violence of an attack).
grin and bear it
suffer pain or misfortune in a stoical manner.
The usual modern sense of grin is less sinister than its earliest senses when it entered the language it primarily meant an act of showing the teeth or a snarl. From the mid 17th century to the mid 18th century, a grin was generally used in a derogatory way or in unfavourable contrast to a cheerful smile. The sense of grin in grin and bear it retains the earlier associations with showing your teeth in a grimace of pain oranger. Grin and abide is recorded as a proverb in the late 18th century; the modern version dates from the late 19th century.
have your cross to bear
suffer the troubles that life brings.
The reference here is to Jesus (or Simon of Cyrene) carrying the Cross to Calvary before the Crucifixion. The image is also used metaphorically in the New Testament (for example, in Matthew 10 : 38 : And he that taketh not his cross and followeth after me is not worthy of me).
like a bear with a sore head
(of a person) very irritable - British informal
loaded for bear
fully prepared for any eventuality, typically a confrontation or challenge - North American informal
The image here may be of a hunting gun loaded and ready to shoot a bear.