Jerry Mouse is one of the two titular main protagonists (alongside Tom Cat) of the Tom and Jerry cartoons. But during the Gene Deitch-era, he is portrayed as extremely unlikable that it's even out of character for him.
Unlike in the classic and Chuck Jones-eras, where Jerry's antagonistic tendencies with Tom were meant to be all play rather than serious attacks while bonding with Tom over a mutual sentiment towards an unpleasant experience, here, he takes it too far by downright making Tom's owner torturing Tom for his own sick amusement while showing absolutely no mercy for Tom. Worst of all, he never gets any comeuppance for his actions (with the minor exception of Calypso Cat), which he occasionally does in the classic and Chuck Jones-eras even whenever he provokes Tom while taking it to the extreme. Jerry may have been troublesome and mischievous, but not to the extent of being malicious and sadistic, making this out of character for him.
He usually has Tom get in to trouble with Tom's overweight abusive owner even though it wasn't his fault.
The injuries that he conflicts on Tom are more lifelike and hurtful rather than being cartoonish and funny.
His flanderization is one of the main reasons why the Gene Deitch-era of Tom and Jerry is poorly received by critics and fans.
The laugh that he makes is very creepy thanks to terrible voice actor Allen Swift.
He wins in every episode of the Gene Deitch-era and with the minor exception of Calypso Cat, he never gets his comeuppance.
This incarnation of Jerry is also repeated by Filmation in The Tom and Jerry Comedy Show in 1980, since that show seems to follow the footsteps of the Gene Deitch-era of Tom and Jerry.
In each short, he never gets punished. That's making him a Karma Houdini.
He has massively redeemed himself back to being the loveable, troublesome, cute, and funny mouse again in future Tom and Jerry cartoons since the Chuck Jones-era.
His character design is still cute as usual.
Buddies Thicker than Water is the only cartoon which he was ever likable in the Gene Deitch-era of Tom and Jerry, as he did help Tom from freezing out in the cold, and his abuse towards Tom in that cartoon is justified because Tom betrayed his kindness by throwing him out into the cold in favor of getting pampered by his thin female owner.
He does get his comeuppance in Calypso Cat as he is being pursued by Tom at the end for sabotaging his relationship with a female cat, much to the point of losing her to a calypso player.