Dialogue: 0,0:02:19.06,0:02:24.80,Default,,0000,0000,0000,,[translation]
若しも、若しも人生をもう一度あれば、全て身やり直し出来れば、
=> If... If it could live (jinsei : "human life", in general) again, if every thing could be redone,
Dialogue: 0,0:02:25.42,0:02:32.40,Default,,0000,0000,0000,,[translation]
人はその葉を?となく??と供に、自分を行ないを悔やむ、嘆く
=> I'm missing some words before the ","

=> Second part, "they would mourn and lament their actions/conduct.
(I'll try ask to a friend to see).
Dialogue: 0,0:02:33.68,0:02:36.99,Default,,0000,0000,0000,,[translation]
だが、コウジは、カブトコウジは違う。
=> But, Kouji... Kouji is different.
Dialogue: 0,0:02:37.51,0:02:39.38,Default,,0000,0000,0000,,[translation]
カブトコウジはくやまない!
=> Kabuto Kouji wouldn't/won't mourn/repent!
Missing a timing here : Yes! I won't be puzzled/I won't puzzle myself! (そうだ!俺は迷わない!)
Dialogue: 0,0:02:45.82,0:02:50.41,Default,,0000,0000,0000,,[translation]
仮令人生が何度やり直せとしても、彼は間違いなく同じ道を歩むこと虞はしない
=> (seems the timing is late of two secondes at the start) Even if human life would be remake/started over/redone many times, he will, without a doubt, walk on the same path (less literal : "following the same path/road") without (any) fear! <= (or "fearing anything")
Dialogue: 0,0:02:51.83,0:02:54.77,Default,,0000,0000,0000,,[translation]
そうだ!何度でも、何度でも命を懸けて、この一発を放つ!
=> Yes! I'll risk my life, over and over, (literally "as long as it's needed")
Dialogue: 0,0:02:54.84,0:02:56.59,Default,,0000,0000,0000,,[translation]
この一発を放つ!
=> to fire this move/shot!
Dialogue: 0,0:02:57.00,0:03:00.55,Default,,0000,0000,0000,,[translation]
それが、このれ、カブトコウジ!
=> This is how I, Kabuto Kouji, am! <= (or "That is me, "Kabuto Kouji")
The second part have some voices covered with the sound-effects so it's pretty hard for me to tell, I'll try ask a friend for this one too, except the last sentence :
Dialogue: 0,0:04:51.95,0:04:54.23,Default,,0000,0000,0000,,[translation]
=> We catched an image of the intruder!
For the third part :
Dialogue: 0,0:07:41.06,0:07:44.33,Default,,0000,0000,0000,,[translation]
その程度の事で、あいつが落ちたが死ないさ。
=> Even if it fail at it, he won't die. <= (literally, "ochiru" is "fall" but can be adapted at "fail").
Hope I'll manage to see my friend online, because unfortunately not very familiar with "Mazinger" and it don't help (maybe he even watched it, as he's a part of Shinsen-Subs).