And speaking of speed and durability.
Isaac is shown to dodge lasers, that is enough to give us the idea of his speed. Certain items allow him to shoot lasers,homing tears and everyone knows brimestonespoon bendernigh impossible to dodge. When it comes to durability, chara's durability is affected by her determination (yes im calling chara 'her'). In this situation where the battle is outside undertaleverse, determination based durability will either not exist or both sides have it. Not to mention Isaac's LV is equal to chara (if he's in the undertaleverse, he can destroy timelines easily) so hurting her would not be a problem.

Actually the outcome is quite correct but the author didnt mention more specificly.
Okay let me start with chara. First of all, y'all wanking chara to the max. Why? You see, the save load ability is controlled by Frisk not chara because in genocide run we play as Frisk with the INFLUENCE of chara. Chara's determination is quite weak compared that to Frisk because she could only ended up being a ghost and communicate with people but not total revival (SAVE LOAD). However, by the end of genocide run s/he is able to possess frisk gaining the kid's LV and DETERMINATION (the 2 important factors of her/his power). With their determination combined and Frisk LV, Chara is now able to destroy timelines.
So how does this affect Isaac?
First of all, we should start comparing their determination and LV. Interestingly, when a person has a higher DETERMINATION than that of the other, the SAVE LOAD RESET ability will be controlled by the first person. This is shown when Frisk fell down to the underground. Flowey tells us that before Frisk's arrival, he is the one that could do all the RESET thing thanks to his determination. But due to Frisk's higher DETERMINATION, flowey loses this ability as Frisk took full control of it. Now lets compare Chara and Isaac determination. We know that determination in undertale is based on someones will to do something. Chara's determination is based on her/his desire to kill everyone in the world both humans and monsters. Basically, it was an upgraded version of genocide frisk's determination which is to kill every monster.
Isaac's determination was based on both his will to get the hell out of the place and eventually to kill everyone he sees including the likes of angels, demons and such. His will to get the hell out is an upgraded version of neutral frisk simply because the basement is FAR scarier and f**ked up than the underground. This easily makes his determination equal to that of Chara. Add that to his desire to kill, Isaac's determknation is officially higher. Now you might argue that Isaac would not have determination due to the fact that the game doesnt have any SAVE LOAD, but here's the thing: DETERMINATION in undertale means the will to do something. This will exists in every single fictional universe including the real universe (us). So we could either say both Isaac and Chara will end up destroying multiple timelines due to both high determination or nothing happens because DETERMINATION wont do anything in Isaac's universe.
Next we compare both LV (level of violence).
By the end of genocide run, Frisk killed a decent amount of monsters until s/he reached LV20 before getting possessed by Chara. We could conclude that LV20 determination multitimeline busting powers in undertale universe. Isaac on the other hand killed a lot of monsters as well and MORE. Assuming that the monsters he killed has souls equivelant to that in undrrtale (1 human soul all monsters soul), Isaac clearly killed the same or more monsters than Frisk. Not to mention, he killed his mom whose a human whose soul is equivalent to all of the monsters in undertale. So basically, after killing mom's heart Isaac's LV is already LV20. Whether or not this LV could increase is debatable but lets just stick to LV20 as maximum LV.
Therefore, we could simply conclude that
Isaac has higher determination and equal LV than that of Chara. Without analysing their arsenals or skills, thsi fact alone is enough to prove that Isaac is stronger than Chara and s/he will not be able to RESET SAVE LOAD due to Isaac's high determination.

So, chara is not that powerful as people expected.
All we need to defeat that kid is to have higher dtermination and LV.

''Bullet: Ok then.

Tech: Chara, honestly tried their best. But in all reality, Chara didn't stand a chance. Analyzing their arsenal, skills, and strengths, Chara didn't come ANYWHERE close to winning.

Bullet: Victory was vaporized before Chara saw it coming. While Isaac's was filled to the BRIMSTONE.

Tech: The winner, is Isaac.'' No. That is not a proper post analysis. You don't go into any detail at all.

While Issac has the means to put down Chara, there is still the SAVE and LOAD abilities. And since the soul SHATTERS before loading, Chara would have loaded. And in the end of the genocide run, Chara attacks Frisk so fast they can't dodge, scaling that to Frisk dodging sunlight from Knight Knight and knowing where Asreil's lightning was going to strike, that attack was faster than light.

This means Chara can both react and attack at lightspeed, putting them above Issac there. Chara isn't physically strong but their soul being the crucial part means Issac's physical attacks would be useless.

Chara also tanked the destruction of Undertale and also did the deed, putting them at planetary if you wanna low-ball it and DIMENSION level if you want to be sensible.

Chara curbstomps.

Awesome and can't wait for you to make this YouTube series! I made my own series to for my Fictional character Collide series! Good luck on it man!